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A  MANUAL  OF 

DETERMINATIVE 
MINERALOGY 


BY 

CHARLES  H.  WARREN,  Ph.D. 

Professor    of   Mineralogy    at    the    Massachusetts    Institute 
of  Technology,  Cambridge,  Mass. 


SECOND  EDITION 


McGRAW-HILL  BOOK  COMPANY,  INC. 

NEW  YORK:  370  SEVENTH  AVENUE 

LONDON:  6  <fc  8  BOUVERIE  ST.,  E.  C.  4 

1922 


»      c    v      c-    ,."+      t     n  »    -. 


SCIENCES 
LIBRARY 


Ceoi. 

COPYRIGHT  1921,  1922,  BY  THE 
McGRAW-HiLL  BOOK  COMPANY,  INC. 


^JO- 


'S  NOTE 


THIS  manual  H  was  originally  written  and  privately  printed 
for  use  in  the  beginner's  course  in  mineralogy  at  the  Massa- 
chusetts Institute  of  Technology.  There  are  several  excellent 
textbooks  covering  elementary  crystallography  and  descriptive 
mineralogy  which  are  quite  satisfactory  in  these  particulars. 
On  the  determinative  side,  in  the  writer's  opinion,  they  leave 
much  to  be  desired.  The  comprehensive  work  by  Brush  and  Pen- 
field  is,  of  course,  an  indispensable  adjunct  to  any  mineralogical 
laboratory,  but  to  require  students  to  purchase  it  in  addition  to  a 
descriptive  textbook  appeared  to  be  asking  a  good  deal  of  them. 
It  was,  therefore,  for  the  purpose  of  enabling  the  student  to 
supplement  his  descriptive  text  and  crystallography  with  a 
relatively  inexpensive  but  satisfactory  determinative  text  that 
this  manual  was  compiled.  Experience  with  its  use,  over  a 
period  of  several  years,  has  demonstrated  that  it  gives  satis- 
factory results  both  as  an  aid  in  the  determination  of  the  more 
common  minerals  and  as  a  means  of  training  the  students  in  the 
systematic  examination  of  mineral  material  generally.  Think- 
ing that  perhaps  other  teachers  of  mineralogy  might  also  find  it 
useful  as  an  auxiliary  text,  the  author  has  arranged  for  its 
publication. 


819521 


AUTHOR'S  NOTE  TO   SECOND  EDITION 


SINCE  this  manual  was  published,  the  author's  attention  has 
been  called  to  the  omission  of  certain  tests  which  might  well  have 
been  included  in  the  text.  They  are  as  follows : 

Flame  Test  for  Manganese. — Manganese  minerals  if  moistened 
with  hydrochloric  acid  and  ignited  B.B.,  or  on  a  platinum  wire  in 
the  Bunsen  flame,  yield  a  yellowish-green  flame  color. 

Test  for  Cerium. — If  a  little  red  lead  is  added  to  a  nitric  acid 
solution,  the  solution  boiled,  and  allowed  to  settle,  it  will  be 
colored  orange  if  cerium  is  present. 

Test  for  Cassiterite,  SnC>2. — Grains  of  cassiterite,  if  put  in  dilute 
hydrochloric  acid  with  a  piece  of  metallic  zinc,  become,  in  a  short 
time,  covered  with  a  gray,  metallic  coating  of  tin. 

Ccesium,  Cs. — Hydrochlorplatinic  acid  added  to  a  hydro- 
chloric acid  solution  containing  caesium,  produces  a  fine  yellow 
precipitate  of 


vi 


LIST  OF  ABBREVIATIONS  USED  IN  THE  TEXT  AND  TABLES 


B.B , Before  the  Blowpipe 

B.  &  P.      ...''. Brush  and  Penfield's 

Determinative  Min- 
eralogy 

Civ Cleavage 

Char Charcoal 

Cmm Cubic  millimeter 

CC Cubic  centimeter 

Cone Concentrated 

Cryst Crystal  or  Crystalline 

C.  T .     .  Closed  Tube 

Diff Difficultly 

F Fusibility 

Gran Granular 

H Hardness 

Hex Hexagonal 

I Isometric 

Isom.  w Isomorphous  with 

Mass Massive 

M Monoclinic 

O Orthorhombic 

O.F Oxidizing  Flame 

O.T Open  Tube 

Perf Perfect 

Pine. Pinacoidal 

Ppt. Precipitate 

Prism Prismatic 

R.F Reducing  Flame 

Rhomb,  or  R Rhombohedral 

Sol Soluble 

Sp.G Specific  Gravity 

T Tetragonal 

Trie Triclinic 

U Usually 

Volt Volatile 

vii 


CONTENTS 


AUTHOR'S  NOTE  : v 

AUTHOR'S  NOTE  TO  SECOND  EDITION vi 

LIST  OF  ABBREVIATIONS vii 

CHAPTER 

I     THE  USE  OF  THE  BLOWPIPE,  ETC 1 

II    SIMPLE  TESTS  FOR  THE  ELEMENTS 22 

III  TABULATED  LISTS  OF  REACTIONS,  ETC.,  USEFUL  IN  DETERMINATIVE 

MINERALOGY 77 

IV  THE  DETERMINATION  OF  MINERALS,  USE  OF  TABLES,  ETC 89 

INDEX .  155 


DETERMINATIVE  MINERALOGY 


CHAPTER  I 
THE  USE  OF  THE  BLOWPIPE,  ETC.* 

Making  the  Blowpipe  Flame. — What  is  known  as  the  "  blue 
cone  "  blowpipe  flame  is  made  by  inserting  the  tip  of  the  blow- 
pipe into  a  small  luminous  gas,  or  a  large  candle  flame,  and 
blowing  through  it  a  steady  current  of  air  from  the  cheeks.  A 
blowpipe  fitted  with  a  small  "  trumpet  "  mouth-piece,  will,  in 
general,  be  found  the  least  tiresome  to  the  lips.  The  pipe  may 
conveniently  be  held  between  the  thumb  and  first  three  fingers 
of  the  right  hand,  the  forearm  being  allowed  to  rest  on  the  edge 
of  the  desk.  This  manner  of  holding  gives  the  greatest  freedom 
for  manipulating  the  pipe,  and  makes  it  easy  to  control  the  direc- 
tion of  the  flame. 

In  blowing,  the  cheeks  are  used  exactly  like  a  pair  of  bellows, 
being  kept  distended  by  a  continuous  supply  of  oxygen-rich  air 
from  the  throat,  regular  breathing  meanwhile  going  on  as  usual. 
With  a  little  practice  it  will  be  found  that  a  continuous  stream 
of  air  under  moderate  pressure  can  be  blown  through  the  pipe 

*  For  a  list  and  description  of  apparatus  and  reagents  desirable  for  work 
in  determinative  mineralogy  reference  may  be  made  to  Brush  &  Penfield's 
"  Determinative  Mineralogy  and  Blowpipe  Analysis." 

Sets  of  Blowpipe  apparatus  for  mineralogy  and  also  for  blowpipe  assay 
work  are  sold  by  The  Marine  Compass  Co.,  Bryant ville,  Mass.;  by  the 
Chemists'  &  Surgeons'  Supply  Co.,  Lim.,  32  McGill  College  Ave.,  Montreal, 
Canada.  Very  complete  outfits  are  also  listed  by  Eimer  &  Amend,  211  Third 
Ave.,  New  York. 


2      ',.;,..,.    DETERMINATIVE  MINERALOGY 

for  some  time.  The  student  should  practice  at  making  this  flame 
until  he  can  maintain  a  steady  flame  having  a  sharply  defined 
blue  cone  about  three  centimeters  long  for  several  minutes.  In 
case  the  blowpipe  gives  an  irregular  and  poorly  shaped  flame,  or 
one  of  improper  length,  the  hole  in  the  pipe  should  be  bored  out 
carefully  with  a  small,  tapered,  steel  reamer. 

In  the  laboratory,  the  ordinary  Bunsen  burner  may  be  adapted 
for  use  with  the  blowpipe  by  slitting  and  opening  the  top  of 
the  tube  on  one  side  for  about  two  centimeters.  The  holes  for 
the  admission  of  air  at  the  base  should  be  kept  tightly  closed. 
In  places  like  the  field,  where  gas  is  not  available,  the  flame  fur- 
nished by  a  thick,  flat,  and  nicely  trimmed  wick,  which  dips 
into  tallow  or  other  hydro-carbon  fuel,  capable  of  yielding  a 
luminous  flame,  rich  in  unburned  hydrocarbon  gases  and  carbon, 
may  be  used. 

The  "Blue  Cone"  Blowpipe  Flame. — The  blowpipe  flame 
made  as  described  above,  like  the  familiar  "  Bunsen"  flame, 
consists  of  three  parts  or  cones,  or  four  if  we  count  an  outer  and 


FIG.  1. — Blue-cone  Reducing  Flame. 

practically  invisible  cone.  Within  the  sharply  defined  "  blue 
cone  "  (at  c,  see  Fig.  1)  is  unburned  hydrogen  and  carbon,  the 
products  of  the  dissociation  of  the  hydrocarbon  fuel,  and  air 


THE  USE  OF  THE  BLOWPIPE,  ETC,  3 

from  the  pipe.  Then  follows  a  very  thin  envelope  (r)  deep 
blue  in  color  in  which  the  combustion  is  very  active  and  is  con- 
cerned chiefly  with  the  burning  of  the  carbon  to  carbon  mon- 
oxide. This,  with  the  hydrogen,  is  carried  on  into  the  next 
cone  (d),  where  the  carbon  monoxide  is  oxidized  to  carbon  dioxide 
and  the  hydrogen  to  water  vapor.  Outside  of  this  cone,  which 
is  not  very  sharply  defined,  we  have  a  zone  of  hot  gas  or  vapor 
which  is  completely  oxidized.  Many  substances  containing 
oxygen,  if  held  in  cone  d,  will  yield  up  part,  or  all,  of  their  oxygen 
under  the  action  of  the  highly  heated  carbon  monoxide  and  be 
reduced,  the  carbon  monoxide  becoming  carbon  dioxide.  This 
part  of  the  flame  is  therefore  called  the  "Reducing  Flame  " 
usually  designated  by  the  abbreviation  R.F. 

EXPERIMENT  No.  1.— Test  a  small  splinter  of  Hematite,  Fe2O3,  with 
a  magnet.  Next  heat  the  splinter  in  the  forceps  B.B,  in  the  reducing  flame 
(in  cone  d,  immediately  beyond  the  point  of  the  blue  cone),  and  after  the 
splinter  has  been  allowed  to  cool,  test  it  again  with  the  magnet.  The  reaction 
is  3Fe2O3+CO  =  2Fe3O4+CO2. 

If  a  substance  capable  of  oxidation  is  heated  at  a  point  about 
three  centimeters  beyond  the  point  of  the  blue  cone,  viz.,  in  the 
outermost  zone  of  the  flame  (at  o),  where  there  cannot  be  reduc- 
ing action  and  where  oxygen  from  the  air  can  and  does  mix  with 
the  hot  gases  of  the  flame,  it  will  take  on  oxygen  and  become 
oxidized.  This  part  of  the  flame  is  therefore  called  the  "  Oxidizing 
Flame,"  usually  designated  by  the  abbreviation  O.F.  The  oxi- 
dizing part  of  the  flame  is  much  cooler  than  the  reducing  flame, 
so  that,  as  a  rule,  it  requires  a  considerably  longer  exposure  in 
this  flame  to  produce  oxidation  than  it  does  to  accomplish  reduc- 
tion in  the  reducing  flame. 

EXPERIMENT  No.  2.— Take  a  splinter  of  Hematite  and  treat  it  as  in 
Exp.  No.  1,  except  that  it  should  be  heated  only  an  instant  in  the  R.F., 
or  just  long  enough  to  render  it  magnetic.  Next  reheat  this  splinter  for 
several  minutes  in  the  O.F.  After  cooling,  test  it  again  with  the  magnet. 
It  should  have  lost  its  magnetic  properties  if  the  oxidation  has  been  com- 
plete. What  is  the  chemical  change  here? 


DETERMINATIVE  MINERALOGY 

The  hottest  part  of  the  flame  is  at  the  point  of  the  blue  cone  r, 
indeed,  the  temperature  is  sufficiently  high  at  this  point  to  melt 
a  small  platinum  wire.  It  should  be  remembered,  however,  that, 
although  the  flame  is  locally  very  hot,  it  is  also  small,  and  the  si;.c 
of  the  fragment  or  assay  which  is  to  be  heated  in  the  flame 
should  be  gauged  accordingly. 

The  Smoky  Reducing  Flame. — If  the  tip  of  the  blowpipe  is 
held  just  outside  of  the  flame,  and  a  gentle  current  of  air  is 
blown  across  and  downward  through  the  flame,  what  is  known 
as  the  smoky  reducing  flame  is  produced.  This  flame  is  somewhat 
luminous,  much  less  sharply  outlined  than  the  other  flame,  and 
is  essentially  a  reducing  flame,  since  it  contains  still  an  excess 
of  unburned  and  partially  burned  carbon.  Although  its  tem- 
perature is  considerably  lower  than  that  of  the  blue-cone  flame, 
it  is,  nevertheless,  on  account  of  its  strong  reducing  qualitites, 
especially  useful  in  operations,  such  as  the  production  of  the 
lead  button  in  the  blowpipe-silver  assay,  where  a  strong  reducing 
action  is  necessary,  but  where  a  very  high  temperature  is  either 
not  needed  or  is  undesirable, 


THE  TESTING  OF  MATERIALS  BEFORE  THE  BLOWPIPE 

Heating  in  the  Platinum  or  Chromel  Forceps.* — By  simply 
heating  small  fragments  held  in  the  forceps  in  the  blowpipe 
flame,  facts  may  be  learned  regarding  substances,  particu- 
larly minerals,  which  are  useful  in  determining  their  identity. 
Indeed  it  may  be  said  that  after  a  study  of  the  purely  physical 
characteristics  of  a  mineral,  the  next  step  towards  its  identi- 
fication is  to  heat  a  fragment  B.B.,  in  the  forceps.  Careful 
observation  of  every  detail  cf  its  behavior  will  very  often  furnish 
useful  information. 

In  performing  this  operation  a  fragment  should  generally  be 

*  Forceps  tipped  with  a  nickel-chromium  alloy  "Chromel"  are  much 
"  cheaper,  and  quite  as  satisfactory  as  those  tipped  with  platinum. 


THE  USE  OF  THE  BLOWPIPE,  ETC.  5 

chosen  about  the  diameter  of  an  ordinary  pencil  lead  and  3  or 
4  mm.  long.  It  is  held  in  the  forceps  so  that  the  greater  portion 
of  it  is  free  of  the  forceps  and  somewhat  inclined  toward  the 
flame.  It  should  then  be  introduced  into  the  cooler  portion  of 
the  flame  first,  and  then,  if  necessary,  moved  up  to  a  position 
very  near  the  point  of  the  blue  cone,  viz.,  the  hottest  part  of  the 
flame.  The  position  of  the  fragment  with  reference  to  the  flame 
is  shown  in  Fig.  1. 

The  more  important  phenomena  that  may  be  observed  in 
this  connection  are:  a,  degree  of  fusibility;  b,  manner  of  fusing; 
c,  decrepitation,  crumbling;  d,  volatility;  e,  changes  of  color, 
glowing;  /,  formation  of  a  strongly  basic  oxide;  g,  flame  colora- 
tions; h,  magnetic  properties. 

(a)  Degree  of  Fusibility. — The  determination  as  to  whether 
a  mineral  can  or  cannot  be  melted  (fused),  and  if  it  can  be,  the 
degree  of  ease  with  which  this  can  be  accomplished,  is  a  matter 
of  the  first  importance  in  the  determination  of  minerals.  For 
purposes  of  easy  comparison  the  so-called  "  scale  of  fusibility  " 
has  generally  been  adopted.  This  scale  is  given  below,  and  con- 
sists of  a  series  of  five  common  minerals,  arranged  in  order  of 
their  apparent  increasing  resistance  to  fusion. 

If  a  mineral  fuses  B.B.  its  ease  of  fusion  is  compared  with 
those  of  the  standard  minerals  of  the  scale,  and  its  relative 
fusibility  thus  determined.  Care  should  be  taken  in  the  case 
of  easily  fusible  or  volatile  compounds,  especially  those  of 
metallic  appearance,  not  to  allow  them  to  melt  on  to  the  forceps, 
particularly  if  platinum  is  used.  Care  should  also  be  taken  to 
have  only  one  end  of  the  fragment  in  the  flame,  so  that  as  little  heat 
as  possible  may  be  conducted  away  by  the  forceps.  If  a  fragment 
of  the  standard  size  suggested  above  is  used,  and  little  or  no 
melting  takes  place,  it  is  well  to  select  smaller,  very  thin  splinters 
and  test  them.  With  minerals  that  fuse  with  great  difficulty, 
such  as  No.  5  of  the  scale,  the  melting  is  generally  only  a  rounding 
of  the  point  or  thin  edges,  and  careful  examination  with  a  hand 
lens  should  be  made  before  and  after  heating.  It  is  obvious  that 
in  comparing  different  minerals  in  regard  to  their  relative  fusi- 


6  DETERMINATIVE  MINERALOGY 

bility  that  fragments  of  as  nearly  the  same  size  and  shape  as 
possible  should  be  chosen. 

For  the  manner  of  handling  minerals  which  decrepitate  B.B., 
see  p.  7. 

Scale  of  Fusibility 

No.  1.     STIBNITE,  Sb2S3. 

Fuses  easily  in  the  luminous  lamp  or  gas  flame.  Fusible 
at  a  low  red  heat  in  the  closed  glass  tube. 

No.  2.  CHALCOPYRITE,*  CuFeS2  or  Natrolite,  Na2Al^isOioi 
2H2O.  Fuses  in  a  luminous  gas  or  lamp  flame.  Fuses  in  the 
closed  tube  at  a  full  red  heat. 

No.  3.  ALMANDITE  (Garnet),  FeaAkCSiO^s.  Fuses  readily 
before  the  blowpipe.  Can  be  fused  without  much  difficulty  into 
a  globule. 

No.  4.  ACTINOLITE,  Ca(Mg,Fe)3(Si03)4.  The  edges  can  be 
readily  rounded  before  the  blowpipe.  Very  thin  splinters  fuse 
to  a  globule. 

No.  5.  ORTHOCLASE,  KAlSisOs.  The  edges  can  be  rounded 
with  some  difficulty;  extremely  thin  splinters  can  be  fused  to  a 
globule  by  long  continued  heating. 

Although  exceedingly  thin  splinters  of  minerals  which  have  a 
higher  melting  point  than  No.  5  of  the  scale  can  sometimes  be 
distinctly  rounded  B.B.,  it  is  customary  in  Determinative  Miner- 
alogy to  class  all  such  as,  "Fusible  above  5,"  or  simply  as 
"infusible,  B.B." 

In  order  to  determine  the  fusibility  of  substances  which  decrep- 
itate when  heated,  they  may  be  finely  powdered,  moistened  to  a 
paste  with  a  little  water,  and  then  heated  on  a  charcoal  support; 

EXPERIMENT  No.  3. — Test  the  fusibility  of  the  minerals  given  in  the 
"scale  of  fusibility."  Make  the  tests  first  with  fragments  of  standard 
size,  then  with  larger  and  smaller  fragments.  Try  very  thin  splinters  with 

*  In  using  this  mineral,  slow  heating  should  be  avoided,  for  this  may 
allow  oxidation  to  take  place,  and  if  this  occurs  to  any  considerable  extent, 
the  fusibility  is  decreased. 


THE  USE  OF  THE  BLOWPIPE,  ETC.  7 

Nos.  4  and  5.  Note  with  No.  1,  Stibnite,  that  it  volatilizes  rapidly  with  the 
formation  of  white  fumes  of  antimony  oxide  and  a  pale  greenish  flame  color. 
Care  should  be  taken  not  to  allow  the  melted  portions  of  this  mineral  to 
touch  the  forceps. 

(b)  Manner    of   Fusing;     intumescence,    swelling,    exfoliation, 
branching,   etc. — Fusion  accompanied  by  more  or  less   boiling  or 
bubbling  (intumescence)  during  a  part  or  all  of  the  period  of 
heating   is  a   peculiarity  of  many  minerals,   particularly  those 
containing    chemically    combined    water    or    other    constituents 
driven  off  during  melting.    The  fused  fragments  of  such  minerals 
are  apt  to  be  scoriaceous  or  full  of  bubbles.     A  few  minerals 
exfoliate  (leaf  out),  or  branch,  or  swell,  either  before  or  during 
fusion. 

EXPERIMENT  No.  4. — Heat  fragments  of  stilbite  and  lepidolite,  noting  in 
the  case  of  the  first,  the  branching  and  intumescence,  in  the  second,  the 
intumescence  and  flame  color,  and  in  both,  the  appearance  of  the  well  fused 
mass. 

(c)  Decrepitation  and  Crumbling. — Many  minerals  decrepitate 
B.B.   and  some,  like  fluorite,  always  decrepitate  when  heated. 
Decrepitation  is  apt  to  occur  with  minerals  containing  liquid 
inclusions,    and    also    in    many    minerals    possessing    excellent 
cleavages.     In  the  latter  case  decrepitation  is  to  be  ascribed  to 
violent  rupture  along  planes  of  weakness  under  the  action  of  the 
stresses  set  up  by  rapid  expansion.     In  many  cases,  however,  the 
decrepitation  seems  to  be  due  to  some  structural  peculiarity  of 
the  individual  specimen,  and  appears  to  be  independent  of  cleav- 
age or  inclusions.     One  specimen  of  chalcopyrite,  for  example, 
will  decrepitate  violently,  while  another  will  show  no  signs  of  it. 

Minerals  which  decrepitate  so  badly  that  fragments  cannot 
be  used  for  testing  their  fusibility,  etc.,  in  the  forceps,  or  that 
fly  from  the  charcoal,  may  either  be  heated  in  a  hard  glass  tube 
(C.T.)  until  dec  epitation  ceases,  or  they  may  be  powdered 
finely  in  a  mortar,  and  then  some  of  the  powder,  thus  obtained, 
may  be  put  on  the  charcoal,  and  after  moistening  with  water, 
may  be  scraped  into  a  compact  little  heap  and  tested  B.B.  as 
desired. 


8  DETERMINATIVE  MINERALOGY 

A  few  minerals,  chiefly  infusible  carbonates  of  the  alkali- 
earth  elements,  or  hydrated  oxides,  powder  or  crumble  B.B. 
Such  behavior  generally  points  to  the  loss  of  some  constituent 
such  as  CO2  or  H^O. 

(d}  Volatilization,  partial  or  complete,  may  occur.  This  is 
generally  accompanied  by  fusion,  though  not  always,  and  since 
it  is  commonly  some  oxide-forming  element  (as  Sb,Pb,S,  etc.), 
evidence  of  such  behavior  is  generally  obtainrd  in  the  fumes 
arising  from  the  fragment,  or  by  a  characteristic  odor,  or  by  a 
flame  color.  In  such  cases  further  tests  on  charcoal,  or  in  the 
open  and  closed  tubes,  are  usually  in  order. 

(e)  Changes  of  Color.  Glowing. — When  minerals  of  non- 
metallic  appearance  turn  black  on  being  heated  B.B.,  it  generally 
indicates  the  presence  of  either  iron,  manganese,  or  copper. 
The  color  assumed  by  a  fragment  after  heating  should  always 
ba  noted. 

With  minerals  of  non-metallic  appearance  we  may  make  the 
following  divisions,  based  on  the  character  of  the  fusion,  which 
are  useful  in  determinative  work  (see  tables  pp.  129-137). 

Minerals  that  fuse  to:  (a)  a  clear  glass. 

(6)  a  white  glass,  or  enamel. 

(c)  a  colored    (yellow-brown-greenish) 

glass,  enamel,  or  slag. 

(d)  a  black  enamel  or  slag. 

Intense  glowing,  or  the  emission  of  a  white  light,  by  the  heated 
fragments  may  in  general  be  taken  as  an  indication  of  great 
infusibility. 

(/)  Formation  of  a  Strongly  Basic  Oxide. — When  fragments 
of  the  carbonates,  sulphates,  and  halogen  salts  of  the  alkali  and 
alkaline-earth  metals  are  heated  intensely  B.B.  they  are,  to  a 
greater  or  less  extent,  decomposed,  yielding  the  oxide.  If  the 
fragment  is  placed  on  a  piece  of  moistened  turmeric  paper  or 
reddened  litmus  paper,  an  alkaline  reaction  (shown  by  a  brown 
(turmeric)  or  blue  (litmus)  coloration  of  the  paper)  will  result,  due 
to  the  formation  of  an  alkaline  hydrate.  As  the  number  of  such 


THE  USE  OF  THE  BLOWPIPE,  ETC.  9 

salts  occurring  as  minerals  is  small,  this  test  is  a  very  useful  one  in 
determining  such  minerals  (see  Table,  p.  128). 

(g)  Flame  Colorations. — Fragments  of  minerals  containing 
one  of  the  elements  yielding  a  characteristic  flame  color  often 
impart  the  color  to  that  portion  of  the  blowpipe  flame  that  shoots 
out  beyond  the  fragment.  Except  in  the  case  of  very  volatile 
metallic  compounds,  and  of  sodium-bearing  minerals  in  general, 
the  coloration  of  the  blowpipe  flame  amounts  to  little  more  than 
a  mere  sliver  of  color  and  may  be  easily  overlooked.  In  some 
cases  strong  and  prolonged  ignition  may  be  required  to  produce 
a  satisfactory  coloration.  Flame  colorations  obtained  from 
fragments  should  generally  be  verified  by  flame  tests  made  as 
described  beyond  under  another  heading,  p.  19.  The  yellow 
flame  of  sodium  is  often  obtained  at  first  with  almost  any  frag- 
ment that  has  stood  about  the  room,  or  been  handled,  but  it 
usually  burns  off  quickly. 

EXPERIMENT  No.  5. — Observe  the  flame  colors  obtained  by  heating 
fragments  of  strontium  sulphate  (celestite)  or  the  carbonate  (strontianite) 
and  barium  carbonate  (witherite)  or  sulphate  (barite)  B.B.  Place  the 
fragments  after  heating  on  a  piece  of  moistened  turmeric  paper  and  note 
the  alkaline  reaction  resulting.  Consider  the  reactions  of  this  experiment. 

(h)  Magnetic  Properties. — In  the  cases  where  the  fragment 
turns  black,  with  or  without  fusion,  it  is  well  to  prolong  the 
heating  in  R.F.,  and  then  to  test  the  cold  sample  with  a  magnet, 
to  see  if  it  is  attracted  by  the  magnet  because  of  the  presence  of 
any  considerable  quantity  of  iron,  or,  more  rarely,  nickel  or  cobalt. 

EXPERIMENT  No.  6. — Heat  a  small  fragment  of  garnet,  for  a  con- 
siderable time  at  the  point  of  the  blue  cone.  Note  that  it  turns  black,  and 
when  cold  can  be  picked  up  with  the  magnet.  Heat  a  fragment  of  sideri'  •, 
FeCO3,  for  a  short  time  B.B.  and  test  the  cold  fragment  with  a  magnet. 


10  DETERMINATIVE  MINERALOGY 


HEATING  BEFORE  THE  BLOWPIPE  ON  CHARCOAL 

Rectangular  blocks  of  compact  charcoal  are  much  used  in 
blowpipe  work  for  various  operations.  These  may  be  summarized 
as  follows : 

(a)  Testing  the  fusibility  of  (1)  metallic  minerals  contain- 
ing volatile  elements  likely  to  injure  the  forceps  and  (2)  of 
powdered  materials. 

(6)  Reduction  of  metals  from  their  minerals  with  and  with- 
out the  aid  of  fluxes. 

(c)  Formation  of  sublimates — chiefly  metallic  oxides  (with  or 
without  the  aid  of  fluxes). 

(d)  Roasting  of  metallic  minerals  to  remove  volatile  oxidiz- 
able  constituents,  such  as  sulphur,  arsenic,  etc. 

(e)  The    decomposition   with    fluxes    of   refractory    silicates, 
oxides,  etc.,  chiefly  in  order  to  render  them  soluble  in  acids. 

(a)  For  simple  fusion  tests,  as  well  as  for  other  operations, 
the  charcoal  stick  is  held  generally  in  a  flat  position  or  one  slightly 
inclined  to  the  horizontal,  and  in  a  position  so  that  the  direction 
of  the  blowpipe  flame  is  with  the  long  way  of  the  coal.  The  flame 
is  directed  so  that  it  strikes  the  surface  at  an  angle  of  about  45°, 
although  this  angle  is  often  varied  considerably,  according  to  the 
requirements  of  any  particular  experiment  or  part  of  an  experi- 
ment. Sometimes,  where  a  fragment  is  to  be  heated,  or  where  a 
very  fluid  melt  or  a  globule  is  likely  to  result,  a  shallow  depression 
is  scraped  in  the  surface  of  the  coal  with  a  knife  or  other  con- 
venient instrument.  In  general,  however,  the  use  of  the  flat 
surface  is  to  be  recommended,  since  with  a  little  practice  no 
difficulty  will  be  found  in  keeping  the  substance  in  place  on  the 
flat  coal,  and  in  cases  where  coatings  may  be  formed,  a  flat  sur- 
face receives  them  much  better,  and  also  permits  of  their  being 
examined  to  better  advantage,  than  one  having  a  hole  in  it.  In 
all  cases  where  a  powdered  material  (with  or  without  fluxes)  is 
to  be  strongly  heated,  it  should  be  previously  moistened  with  a 
little  water,  just  sufficient  to  hold  the  powder  together  and  pre- 


THE  USE  OF  THE  BLOWPIPE,  ETC.  11 

vent   its   being   blown    away    before   sintering   or  fusion   takes 
place. 

(6)  Reduction  of  Metals. — Certain  metals,  notably  gold, 
silver,  copper,  and  lead,  may  be  reduced  from  some  of  their 
minerals  without  difficulty  by  heating  alone  in  the  R.F.  In 
general,  the  operation  of  reduction  is  considerably  facilitated 
by  mixing  sodium  carbonate,  borax,  or  borax  glass  (rarely  other 
fluxes  are  used)  and  powdered  charcoal  (scraped  from  the  surface 
of  the  charcoal)  with  the  powdered  mineral.  The  charcoal  of 
course  acts  as  a  strong  reducing  agent.  The  fluxes  often  act 
simply  as  mechanical  aids  and  as  absorbers  of  impurities,  but 
also  in  some  instances  react  chemically  with  the  substance.  In 
many  instances  the  presence  of  both  the  flux  and  charcoal  is 
necessary  in  order  to  obtain  a  successful  reduction.  The 
quantity  of  flux,  etc.,  required  will  vary  with  different  minerals 
and  no  general  statement  can  be  made  regarding  it.  Such  de- 
tails will  be  given  in  the  text  as  occasion  demands.  In  any 
case  a  quantity  of  the  mineral  powder  should  be  taken,  such  that, 
when  mixed  with  the  flux,  moistened  with  water,  and  scraped 
into  a  compact  little  mass  on  the  coal,  it  can  be  easily  covered 
with  the  hot  reducing  part  of  the  flame,  otherwise  much  energy 
and  time  may  be  wasted  trying  to  do  something  beyond  the 
capacity  of  the  blowpipe  flame.  In  preparing  minerals  for 
reduction  or  decomposition,  care  should  always  be  taken  to 
grind  them  finely.  Generally  the  "  blue-cone"  reducing  flame 
is  used  for  reductions  and  decompositions.  In  certain  opera- 
tions, however,  such  as,  for  example,  the  reduction  of  the  large 
lead-silver-button  in  the  "  silver  assay,"  where  it  is  important 
to  keep  the  whole  mass  of  the  assay  entirely  in  a  reducing  atmos- 
phere but  where  very  intense  heating  is  not  necessary,  the 
"  smoky  "  reducing  flame  is  used.  (For  a  list  of  metallic  globules, 
see  table,  p.  77.) 

EXPERIMENT  No.  6. — Try  reducing  a  copper  globule  from  a  small  frag- 
ment of  Malachite,  CuCO3  •  Cu(OH)2,  B.B.  in  the  R.F.  Moisten  2  or  3  cmm. 
of  the  powdered  mineral  and  reduce.  Mix  about  the  same  amount  with  an 
equal  amount  of  borax,  moisten  and  reduce  to  a  copper  globule. 


12  DETERMINATIVE  MINERALOGY 

(c)  Formation  of  Sublimates.* — Many  minerals  yield,  either 
when  heated  on  charcoal  B.B.  alone  or  with  fluxes,  a  character- 
istic sublimate  which  condenses  on  the  flat  surface  of  the  coal  at 
varying  distances  from  the  assay,  depending  on  the  volatility  of 
the  compound  deposited  and  the  size  of  the  flame  used.  The 
sublimates  may  result  in  several  ways;  the  compound  may  vola- 
tilize and  deposit  unchanged  (rare);  a  volatile  oxide  may  form 
and  deposit  (Exp.  No.  7) ;  or  a  reduced  metal  may  itself  volatilize 
B.B.,  and  uniting  with  oxygen  from  the  air,  may  settle  on  the  coal 
(Exp.  No.  8);  or  we  may  have  a  combination  of  the  last  two 
processes  (Exp.  No.  9). 

A  sublimate  should  always  be  examined  as  to  its  color,  both 
when  hot  and  cold,  its  distance  from  the  assay,  and  its  volatility 
in  both  oxidizing  and  reducing  flames  (measured  by  the  ease  and 
rapidity  with  which  the  sublimate  can  be  made  to  disappear  from 
before  the  flame),  and  also  as  to  any  coloration  it  may  impart  to 
the  flame. 

All  charcoal  leaves  some  ash  when  burned.  This  ash,  which 
is  almost  always  white,  but  rarely  brown  or  reddish,  forms  on 
the  surface  of  the  charcoal  block  immediately  about  the  assay 
where  the  flame  strikes  the  coal.  This  coating  of  ash  is  often 
mistaken  by  beginners  for  a  sublimate.  It  is,  however,  a  very 
thin  coat,  retains  in  some  measure  a  structure  derived  from  the 
original  charcoal,  and  is  non-volatile  even  on  the  strongest  heat- 
ing in  the  R.F.  All  white  oxide  sublimates  are  volatile  in  the 
R.F. 

*  The  "PLASTER  TABLET."  Where  strongly  colored  sublimates,  par- 
ticularly such  as  those  obtained  from  certain  metals  when  heated  with  a  mix- 
ture of  equal  parts  of  potassium  iodide  and  sulphur  (see  page  83),  are  to  be 
examined,  a  plate  or  tablet  made  of  plaster  of  Paris  is  used  instead  of  the 
charcoal.  The  colors  of  the  sublimate  contrast  strongly  with  the  white  of 
the  tablet  and  many  striking  tests  may  be  obtained  in  this  way.  The  tablets 
may  be  very  easily  made  by  pouring  plaster  of  Paris  mixed  to  a  rather  thin 
paste  with  water,  over  a  glass  plate,  and  while  still  quite  soft,  dividing  the 
plaster  with  a  knife  into  little  rectangles  If  in.  by  3  in.  When  hard  they  can 
be  easily  slipped  from  the  glass. 


THE  USE  OF  THE  BLOWPIPE,  ETC.  13 

EXPERIMENT  No.  7. — Heat  a  fragment  of  molybdenite,  MoS2,  B.B.  in 
the  R.F.  Next  heat  a  fragment  B.B.  for  some  time  in  a  strong  O.F.  Heat 
the  sublimate  last  obtained  in  a  mild  R.F.  (the  Bunsen-burner  flame  answers 
nicely).  Note  the  colors  obtained  and  that  the  coating  is  volatile. 

EXPERIMENT  No.  8. — Mix  thoroughly  3  or  4  cmm.  of  finely  powdered  cas- 
siterite,  SnOa,  with  at  least  one  volume  of  charcoal  dust  and  about  two  of 
soda,  moisten  and  heat  B.B.  in  the  R.F.,  remove  the  globule  obtained  to  a 
small  hole  in  a  clean  surface  of  the  coal  and  heat  it  strongly  in  the  O.F. 
Note  that  the  tin  itself  is  volatile. 

EXPERIMENT  No.  9. — Heat  a  little  powdered  cemssite,  PbCO3,  B.B.  in 
the  R.F.  Test  the  volatility  in  O.F.  and  R.F.  Note  changes  in  color  on 
cooling.  Moisten  the  coating  formed  with  a  drop  of  HI  solution,  and  heat 
gently  in  a  small  O.F. 

(d)  Roasting. — The  term  roasting  is  used  to  designate  the 
process  of  removing  through  oxidation  and  volatilization  one 
or  more  constituents  of  a  mineral.  These  are  usually  either 
arsenic,  antimony,  or  sulphur.  Where  the  mineral  is  not  too 
fusible,  the  roasting  may  be  most  easily  accomplished  by  spread- 
ing the  fine  powder  out  thinly  on  a  flat  charcoal  surface  and 
heating  it  very  gently  in  a  small  oxidizing  flame  until  oxidation 
is  complete.  Any  fusion  of  the  assay  should  be  avoided  if  possible, 
since  fusion  diminishes  the  amount  of  surface  exposed  and  impris- 
ons the  element  within  the  fused  parts.  Toward  the  end  of  the 
operation  the  heat  may  generally  be  increased.  With  very 
fusible  compounds,  such  as  certain  minerals  containing  antimony, 
the  fused  mineral  is  heated  strongly  in  the  oxidizing  flame  until 
most  of  the  volatile  element  is  removed.  The  globule  thus 
obtained  is  then  crushed,  spread  out  on  the  coal  and  roasted  as 
first  described.  The  thoroughly  roasted  product  is  generally  an 
oxide  and,  as  such,  is  often  in  a  more  suitable  form  for  reduction 
with  fluxes  to  a  metallic  globule,  for  bead  tests,  etc.  Roasting 
may  also  be  conveniently  performed  in  the  open  glass  tube  (see 
beyond). 

EXPERIMENT  No.  10. — Mix  3  or  4  cmm.  of  chalcopyrite,  CuFeS2,  with 
two  volumes  of  soda  and  some  charcoal  and  try  to  reduce  a  copper  globule 
from  it.  A  brittle,  black  globule  and  not  metallic  copper  will  be  obtained. 
Next,  roast  thoroughly  about  3  or  4  cmm.  of  the  chalcopyrite  as  described 


14  DETERMINATIVE  MINERALOGY 

above.     Then  mix  with  equal  volumes  of  soda  (or  borax)  and  charcoal  as 
before  and  reduce  to  a  globule. 

EXPERIMENT  No.  11. — Roast  a  little  niccolite,  NiAs,  and  note  the  color  of 
the  residue. 

(e)  Decomposition  of  Insoluble  Minerals  with  Fluxes. — Minerals, 
chiefly  silicates  and  oxides,  which  are  slightly  or  wholly  unaffected 
by  treatment  with  acids  may  be  brought  into  a  condition  per- 
mitting solution  by  first  fusing  them  with  some  flux.  This  fusion 
may  be  performed  satisfactorily  on  charcoal,  B.B.,  or  if  at  hand, 
a  platinum  capsule  made  from  a  small  piece  of  foil  may  be  used, 
the  Bunsen  flame  or  a  blast  supplying  the  heat.  A  large  loop  of 
platinum  wire  bent  back  on  itself  may  also  be  used  to  support 
the  fusion.  This  is  often  the  best  method  to  follow  where  the 
amount  of  mineral  available  is  very  small.  Sodium  carbonate 
(dry)  is  generally  used,  but  borax  or  borax  glass,  potassium 
bisulphate,  or  sodium  peroxide  may  be  used  where  soda  fails. 
In  general,  from  five  to  six  volumes  of  the  flux  to  one  of  the 
mineral  should  be  used. 

EXPERIMENT  No.  12. — Carry  out  an  experiment  on  the  decomposition  of 
ilmenite.  FeTi03,  with  soda  as  directed  under  titanium,  1,  p.  69. 

EXPERIMENT  No.  13. — Mix  thoroughly  4  or  5  cmm.  of  finely  ground 
garnet  with  about  5  volumes  of  sodium  carbonate.  Moisten  to  a  paste  with 
water  and  fuse  to  a  slag,  heating  the  assay  for  several  minutes.  Crush  the 
resulting  fusion  and  dissolve  in  about  5  cc.  of  6N-HNOs  in  a  test-tube  (if 
charcoal  is  mixed  with  fusion  it  should  be  filtered  off  after  solution  is  com- 
plete) .  Finally  evaporate  the  solution  in  the  test-tube  until  gelatinous  silica 
separates. 

Bead  Tests. — A  limited  number  of  elements,  when  their  com- 
pounds are  dissolved  in  fused  borax,  salt  of  phosphorus  (micro- 
cosmic  salt),  or  soda,  impart  characteristic  colors  to  the  flux, 
which  serve  to  distinguish  these  elements.  The  colors  observed 
usually  vary  more  or  less  with  the  state  of  oxidation  of  the  element, 
so  that  different  colors  may  be  obtained  according  as  the  reduc- 
ing or  oxidizing  flame  is  used.  The  colors  also  often  change  as 
the  fusion  cools. 

In  making  use  of  these  color  reactions  a  bead  of  the  fused 


THE  USE  OF  THE  BLOWPIPE,  ETC.  15 

salt  is  made  on  a  loop  of  platinum  wire.  The  wire,  which  should 
be  about  No.  28,  standard  gauge,  may  be  sealed  into  the  end  of  a 
short  piece  of  glass  tubing  to  serve  as  a  holder.  The  loop  may 
conveniently  be  made  by  bending  the  wire  about  a  pencil  end. 
Be  sure  that  the  wires  touch  where  the  end  crosses  over.  The 
loop  should  finally  be  circular  in  shape  and  about  3  mm.  in  diam- 
eter for  most  bead  tests.  A  larger  bead  cannot  be  so  easily 
covered  by  the  reducing  flame,  while  with  one  much  smaller,  it 
is  harder  to  see  the  color,  and  the  amount  of  the  substance  tested 
is  apt  to  be  relatively  too  large. 

Borax  and  salt  of  phosphorus  may  be  made  to  adhere  to  the 
loop  by  simply  heating  it  in  the  flame,  and  then,  while  hot,  dipping 
it  into  the  salt.  The  borax  may  be  fused  without  trouble  to  a 
transparent,  colorless  glass.  Salt  of  phosphorus  becomes  very 
liquid  when  first  heated,  and  in  order  to  keep  it  on  the  wire,  it 
should  be  fused  just  above  the  blowpipe  flame,  so  that  the  upward 
current  of  hot  air  from  the  flame  will  support  it  until  the  volatile 
part  is  removed  and  the  bead  becomes  less  liquid.  If  a  Bunsen 
flame  is  at  hand,  the  salt  of  phosphorus  bead  can  be  easily  made 
by  holding  it  about  one-half  inch  above  the  tip  of  the  blue 
cone.  This  bead  is  also  clear  and  colorless  when  cold.  Soda 
is  most  easily  gotten  onto  the  wire  by  wetting  the  loop  in 
the  mouth,  sticking  it  into  the  powdered  salt,  and  then  fusing  it. 
This  bead  is  clear  when  hot,  but  becomes  white  and  opaque  on 
cooling. 

After  the  bead  is  made,  it  is  touched,  while  still  hot,  to  a 
minute  amount  of  the  finely  powdered  substance,*  and  heated  suc- 
cessively in  the  reducing  and  oxidizing  flames  of  the  blowpipe 
(not  the  Bunsen  burner).  To  get  the  best  reducing  effect  the 
bead  should  be  heated  as  hot  as  possible  at  the  point  of  the  blue 
cone  for  a  short  time,  and  then  by  moving  the  blowpipe  back 
a  little,  at  the  same  time  easing  up  on  the  blast,  the  extremely 

*  Where  arsenic  or  antimony  are  present,  it  is  necessary,  in  order  to  pre- 
vent the  destruction  of  the  platinum  wire,  to  roast  the  mineral  very  thor- 
oughly as  directed  on  p.  13  and  then  test  the  remaining  oxides  in  the  bead. 
It  is  also  better  to  roast  sulphides  previous  to  testing  in  the  bead. 


16  DETERMINATIVE  MINERALOGY 

hot  bead  may  be  entirely  covered  for  a  time  by  the  "  smoky  " 
(carbon  rich)  reducing  flame.  In  oxidizing  a  bead  it  should  be 
heated  for  several  minutes,  since  the  oxidizing  flame  is  not  as  hot 
as  the  reducing  flame,  and  the  reaction  generally  takes  a  longer 
time.  In  general,  it  is  best  to  start  with  a  very  small  speck  of  the 
"  unknown,"  and  then  increase  the  amount  gradually  until  enough 
is  dissolved  in  the  bead  to  give  a  decisive  color.  The  heating  in 
both  flames  should  always  be  repeated,  so  as  to  be  sure  that  the 
color  or  colors  are  constant,  and  care  should  be  taken  to  watch 
for  a  change  of  color  while  the  bead  is  cooling,  and  until  it  is 
perfectly  cold.  When  a  bead  is  obtained  which  is  too  dark  to 
show  the  color  distinctly,  its  true  color  by  transmitted  light  may 
be  seen  by  crushing  the  bead  and  noting  the  color  of  the  powder. 
A  list  of  "  bead  "  reactions  will  be  found  on  pages  83-85. 
This  includes  only  such  as  experience  has  shown  to  be  perfectly 
reliable  in  the  hands  of  the  average  manipulator,  provided  the 
suggestions  made  above  are  followed.  Many  of  the  "  bead  " 
tests  given  in  the  more  extended  lists  to  be  found  in  other  texts 
are  of  very  doubtful  value.  The  following  experiments  will 
illustrate  several  of  the  more  important  bead  reactions.  It  may 
be  remarked  that  "  bead  "  tests  are  often  particularly  useful  as 
confirmatory  tests  with  minerals,  and  with  final  precipitates, 
especially  small  ones  obtained  in  the  course  of  a  qualitative 
analysis. 

EXPERIMENT  No.  14. — Introduce  a  very  little  of  powdered  pyrolusite, 
MnC>2,  into  a  borax  bead  and  heat  B.B.,  first  in  the  hottest  part  of  the  flame, 
until  the  mineral  is  entirely  dissolved,  then  in  the  O.F.  Note  the 
color  when  cold.  Next  heat  it  as  hot  as  possible  in  the  clear  R.F.  for  a 
short  time,  and  then  cover  the  bead  with  the  smoky  R.F.  The  bead  should 
be  colorless  on  cooling. 

EXPERIMENT  No.  15. — Make  a  salt  of  phosphorus  bead  test  with  vanadi- 
nite,  lead  vanadate,  using  a  small  amount  of  the  salt  first  and  then  increasing 
it.  Use  both  O.F.  and  R.F.  Make  similar  tests  with  wulfenite,  PbMoO4, 
and  chromite,  FeCr2O4. 

Heating  in  the  Closed  Glass  Tube. — Tubes,  closed  on  one  end, 
are  made  by  first  heating  a  piece  of  thin- walled,  hard  glass  tubing, 


THE  USE  OF  THE  BLOWPIPE,  ETC.  17 

of  twice  the  required  length,  in  the  middle,  in  a  blast  lamp  or 
good  Bunsen  flame.  When  quite  soft  it  is  taken  out  of  the  flame, 
pulled  out,  and  the  capillary  ends  of  each  half  nicely  sealed  off 
close  up  to  the  end.  The  tubes  should,  for  most  purposes,  be 
from  3  to  4  mm.  internal  diameter  and  about  8  cm.  long. 

Closed  tubes  (C.T.)  are  used  chiefly  to  ascertain  whether  or 
not  a  substance  is  decomposed  or  changed  in  any  way  by  heat 
alone.  They  are  occasionally  used  in  making  fusions  with  fluxes, 
and  then  a  tube  of  larger  diameter  is  desirable,  or  sometimes  one 
with  a  small  bulb  blown  on  the  end  is  used. 

In  closed  tube  tests  a  few  small  fragments,  say  a  millimeter 
in  diameter,  or  with  very  refractory  materials  a  little  of  the  powder, 
are  shaken  down  into  the  end  of  the  tube,  which  is  heated  some- 
what gradually  to  the  full  heat  of  a  Bunsen  flame,  or  to  that  of 
the  blowpipe  flame,  where  the  former  fails  to  produce  any  change. 

Decomposition  may  be  indicated  by  a  change  of  color  in  the 
material,  or  by  the  formation  of  a  sublimate,  solid  or  liquid,  or  by  a 
vapor  in  the  cooler  part  of  the  tube.  A  full  list  of  closed  tube 
reactions  will  be  found  on  pages  78-79. 

Substances  which  decrepitate  may  be  heated  in  the  C.T. 
until  decrepitation  ceases  and  the  resulting  powder  may  then  be 
safely  tested  on  charcoal. 

The  amount  of  oxygen  contained  in  the  tube  is  so  small  that 
its  action  is,  in  general,  negligible,  although  in  a  few  instances, 
such  as  with  the  antimony-sulphur  minerals,  its  action  is  impor- 
tant. 

EXPERIMENT  No.  16. — (a)  Heat  a  fragment  of  siderite,  FeCO3,  in  a 
closed  tube.  Note  the  change  of  color  and  test  the  residue  with  a  magnet. 
If  a  drop  of  barium  hydroxide  be  put  in  the  upper  part  of  the  tube  before 
heating,  a  white  precipitate  of  barium  carbonate  will  be  formed  in  the  drop 
by  the  absorption  of  the  CC>2  given  off  by  the  carbonate.  This  is  a  general 
reaction  with  carbonates.  (6)  Next,  heat  fragments  of  malachite,  CuCO3- 
Cu(OH)2  (blackening  of  residue  and  sublimate  of  water),  (c)  Heat  a  few  frag- 
ments of  gypsum,  CaSO4  •  2H2O,  in  a  closed  tube.  Do  the  same  with  brucite, 
Mg(OH)2.  Compare  the  relative  amount  of  heating  required  in  each  case 
to  expel  the  water.  In  the  first  case  the  water  is  "water  of  crystallization," 
that  is,  water  taken  on  during  the  crystallization  of  the  substance.  In  the 


18  DETERMINATIVE  MINERALOGY 

second,  the  water  is  chemically  combined  and  is  therefore  "  water  of  com- 
position," or  "hydroxyl."  (d)  Heat  fragments  of  pyrite,  FeS2,  and  arsenopy- 
rite,  FeAsS,  separately  in  closed  tubes.  In  each  case,  after  thorough  heating, 
break  off  the  end  of  the  tube  by  touching  it,  while  still  hot,  with  a  drop  of 
water,  and  test  the  residue  with  a  magnet. 

The  reactions  taking  place  in  each  case  are  shown  by  the  following  equa- 
tions: 

(a)  FeCO3  =  FeO+CO2. 

(6)  CuCO3-Cu(OH)2  =  2CuO+CO2-f-H2O. 

(c)  CaSO4-2H2O  =  CaS04+2H2O. 
Mg(OH)2  =  MgO+H2O. 

(d)  FeS2  =  FeS+S. 
FeAsS  =  FeS+As. 

Heating  in  the  Open  Glass  Tube.— The  "  open  tube  "  (O.T.) 
is  a  hard  glass  tube,  from  15  to  17  cm.  long,  with  an  internal  diam- 
eter of  from  5  to  7  mm.  The  substance  to  be  heated  in  the  tube 
should  in  general  be  powdered,  and  is  placed  some  4  or  5  cm.  from 
one  end.  A  neat  and  convenient  way  of  getting  the  powder  into 
the  tube  is  to  put  it  in  the  end  of  a  small  V-shaped  piece  of  paper 
which  is  then  introduced  into  the  tube  and  turned  over.  By  this 
means  the  powder  is  all  deposited  in  a  single  small  heap.  4  or 
5  cmm.  of  material  is  usually  amply  sufficient,  and  exceedingly 
small  amounts  may  often,  with  care,  be  made  to  yield  decisive 
results. 

The  tube,  held  in  an  inclined  position  (say  20°),  is  heated  in 
the  Bunsen  flame,  first  above  the  assay,  so  as  to  start  a  good  current 
of  air  through  the  tube.  If  the  tube  softens,  it  may  be  bent  a 
little,  thus  making  it  easier  to  keep  the  powder  from  slipping  out. 
The  assay  is  next  heated  intermittently  and  very  gently  for  some 
time,  then  more  and  more  steadily  to  the  full  heat  of  the  flame. 
When  very  volatile  substances  are  given  off,  HgS  or  As,  for 
example,  very  slow  and  cautious  heating  may  be  necessary 
throughout  the  test.  If  the  mineral  thus  heated  in  contact  with  a 
current  of  air  contains  an  element  which  forms  a  volatile  oxide, 
the  latter  will  either  pass  out  of  the  end  of  the  tube,  where,  as 
in  the  case  of  sulphur,  it  may  be  detected  by  its  odor,  or  it  may 
condense  as  a  sublimate  with  a  characteristic  appearance  on  the 


THE  USE  OF  THE  BLOWPIPE,  ETC.  19 

cooler  parts  of  the  tube.  A  sublimate,  if  desired,  may  be  collected 
and  tested  further.  If  the  heating  or  "  roasting  "  is  continued 
long  enough,  a  residue  of  metallic  oxide  or  oxides  usually  results, 
and  this,  if  it  possesses  no  characteristic  appearance  to  identify  it, 
is  in  a  favorable  condition  for  examination  by  means  of  bead  tests 
or  otherwise. 

For  a  list  of  Open  Tube  Reactions,  see  pp.  79-81.  The  fol- 
lowing tests  will  serve  to  illustrate  open  tube  reactions: 

EXPERIMENT  No.  17. — Heat  a  little  powdered  galena,  PbS,  in  the  open 
tube  as  directed  above.  Notice  that  the  SO2  is  given  off  at  the  end  of  the 
tube  and  the  lead  is  oxidized  to  lead  oxide,  PbO,  which  is  deep  yellow  when 
hot,  fading  out  to  nearly  white  on  cooling  (PbS +3  O  =  PbO  +SO2) .  If  heated 
rapidly,  PbO  and  SO2  combine  to  form  some  volatile  white  compound,  which 
condenses  on  the  under  side  of  the  tube.  Another  reaction  may  occur,  to  a 
slight  extent,  as  follows:  PbO+SO2  =  Pb+SO3,  resulting  in  tiny  globules  of 
lead. 

EXPERIMENT  No.  18. — Heat  in  an  O.T.  a  little  powdered  niccolite,  NiAs. 
Examine  the  crystalline  sublimate  with  a  lens. 

EXPERIMENT  No.  19. — Do  the  same  with  arsenopyrite,  FeAsS,  heating 
very  slowly  and  cautiously. 

Flame  Tests. — As  has  been  noted  earlier,  flame  colorations 
may  be  obtained  from  a  number  of  minerals  by  simply  heating  a 
fragment  B.B.  While  the  flame  colors  thus  obtained  are  often 
strong  enough  to  be  decisive  tests  there  is  quite  as  often  soire 
uncertainty  about  them.  A  number  of  minerals  which  do  not 
yield  a  flame  color  in  this  way  can  be  made  to  yield  good  flames 
by  one  of  the  following  methods: 

(1)  Heating  on  a  Fine  Platinum  Wire. — A  fine  and  perfectly 
clean  platinum  wire  is  moistened  in  water  and  dipped  lightly 
in  a  bit  of  the  very  finely  powdered  mineral.  The  wire  with  a 
little  adhering  powder  is  then  heated  in  the  edge  of  the  Bunsen 
flame,  about  2  cm.  above  the  end  of  the  tube.  By  using  hydro- 
chloric acid  or,  less  commonly,  sulphuric  acid  (the  latter  with 
phosphates)  in  place  of  water  the  flame  color  may  be  greatly 
intensified.  This  is  particularly  true  of  calcium,  strontium, 
barium,  and  copper. 


20  DETERMINATIVE  MINERALOGY 

(2)  By  Injecting  Some  of  the  Fine  Powder  into  the  Bunsen 
Flame. — This  may  be  most  easily  accomplished  by  holding  the 
steel  mortar,  in  which  the  mineral  is  powdered,  close  to  the  air 
hole  near  the  base  of  the  Bunsen  burner,  and  puffing  a  little  of 
the  fine  dust  into  the  hole  by  pushing  the  pestle  suddenly  into  the 
mortar;  or  the  fine  powder  may  be  blown  into  the  hole,  or  directly 
into  the  flame,  by  a  jet  of  air  from  the  blowpipe  directed  across  a 
bit  of  paper  on  which  some  of  the  powder  has  been  placed. 

Treatment  with  Acids,*  etc. — In  testing  minerals  in  the  wet 
way  it  is  generally  most  convenient  to  use  a  test-tube.  Usually 
about  0.1  to  0.2  gram  of  the  finely  ground  mineral  may  be  recom- 
mended, while  the  amount  of  acid  or  other  solvent  should  not,  in 
general,  exceed  5  to  10  cc.  Where  it  is  found  necessary  to  use  larger 
quantities,  the  operations  are  better  carried  on  in  a  small  casserole. 

Although  few  minerals  are  appreciably  dissolved  by  water 
alone,  it  is  well,  if  the  mineral  is  soft,  to  test  its  solubility  in  water. 
The  great  majority  of  solubility  tests  are  performed  with  dilute 
hydrochloric  or  nitric  acid,  or  both  successively.  If  no  action  is 
noted  with  cold  acid,  the  tube  is  heated  gradually  to  boiling. 

If  the  mineral  goes  into  solution  with  the  evolution  of  a  gas, 
the  latter  is  usually  carbon  dioxide,  CC>2,  but  it  may  be  hydrogen 
sulphide,  B^S,  chlorine  or  an  oxide  of  nitrogen.  H^S  may  be 
recognized  by  its  characteristic  odor,  or  tested  for  by  holding  a 
piece  of  filter  paper  moistened  with  lead  acetate  solution  in  the 
end  of  the  test-tube  (blackens).  Chlorine  may  also  be  recognized 
by  its  odor  and  by  its  bleaching  action  on  moistened  litmus  paper. 
Oxides  of  nitrogen  appear  as  brown  fumes  (dioxide)  above  the 
surface  of  the  liquid.  To  test  for  C02,  see  p.  34. 

*  More  experiments  can  of  course  be  carried  out  to  illustrate  the  tests 
described  under  the  various  headings  of  this  chapter  if  it  is  felt  desirable  to 
do  so.  It  has  long  been  the  practice  of  the  author  to  make  the  preliminary 
work  as  brief  as  possible,  using  it  only  to  introduce  the  student  to  the  type 
tests.  Later  an  abundance  of  tests  are  carried  out  in  connection  with  the 
study  of  the  various  mineral  species.  By  this  procedure  the  tests  have  a 
direct  and  obvious  purpose  and  the  work  is  rendered  more  interesting,  and 
has  a  greater  instructional  value,  besides  affording  adequate  practice  in 
manipulation. 


THE  USE  OF  THE  BLOWPIPE,  ETC.  21 


CO2  indicates  a  carbonate;  EbS,  a  sulphide;  chlorine  some 
higher  oxide  of  manganese;  oxides  of  nitrogen  point  to  an  oxi- 
dizing action,  such  as  results  from  the  action  of  nitric  acid  on  a 
metal  or  metallic  sulphide.  Care  should  be  taken  not  to  confuse 
the  bubbling  of  the  solution  due  to  boiling,  with  effervescence 
proper.  On  taking  the  tube  out  of  the  flame  boiling  ceases  almost 
immediately,  while  effervescence  continues  for  some  moments. 

If  the  mineral  passes  into  solution  without  effervescence,  the 
solution  should  be  evaporated  nearly  to  dryness  to  see  if  gelatinous 
silica  will  separate.  In  order  to  carry  the  silica  test  further, 
see  p.  57. 

If  the  mineral  is  non-metallic  in  character,  and  it  is  suspected, 
either  because  the  color  of  the  acid  or  the  appearance  of  the  powder 
has  changed,  that  the  mineral  has  decomposed  with  the  separation 
of  an  insoluble  residue  (usually  silica),  the  solution  may  be  filtered 
off  and  tested  for  bases  with  appropriate  reagents.  See  p.  58,  §  4. 

Few  metallic  or  submetallic  minerals  that  are  appreciably 
soluble  in  dilute  acids  yield  a  residue,  and  need  not  be  considered 
here. 

Metallic  or  submetallic  minerals,  when  unaffected  by  treat- 
ment with  dilute  acids,  should  be  treated  with  strong  nitric  acid 
(Sp.G.  1  .42)  and  heated.  With  metals,  or  compounds  of  the  metals, 
containing  sulphur,  arsenic,  or  antimony,  oxidation  accompanied 
by  solution,  or  the  formation  of  an  insoluble  compound,  or  by 
both,  results,  and  reddish-brown  fumes  of  nitric  oxide  are  given 
off.  For  a  list  of  residues  that  may  be  obtained  by  such  treat- 
ment, also  for  colors  imparted  to  solutions  by  certain  metals, 
see  p.  88. 

When  the  mineral  is  found  to  be  nearly  or  wholly  insoluble,  it 
may  usually  be  obtained  in  solution  by  fusion  (see  p.  14)  and 
subsequent  treatment  of  the  fusion  with  acids. 


CHAPTER  II 
SIMPLE  TESTS  FOR  THE  ELEMENTS 

For  convenience  in  the  matter  of  reference  the  elements  will  be  taken  up 
in  alphabetical  order.  The  atomic  weight  of  each  element  is  given  after  the 
name. 

Aluminium,  Al — 27.1 

1.  Test  with  Cobalt  Nitrate. — This  test  is  applicable  only  to 
those  minerals  which  are  infusible  and  white,  or  which  become 
white   on   ignition.     The  fragment  or  powder  moistened   with 
cobalt  nitrate  solution  and  intensely  ignited  for  some  time  B.B. 
assumes  a  fine  blue  color. 

Fusible  minerals  and  fluxes,  when  moistened  with  cobalt 
nitrate  and  ignited,  often  assume  a  blue  color,  whether  aluminium 
is  present  or  not,  and  cannot  therefore  be  tested  for  aluminium 
in  this  way. 

Silicate  of  zinc,  calamine,  when  treated  similarly  assumes  a 
blue  color  (see  page  86),  which  should  not  be  mistaken  for  an 
indication  of  aluminium. 

2.  Precipitation    with     Ammonium     Hydroxide. — Aluminium 
hydroxide,  Al(OH)s,  is  thrown  down  from  solutions  of  aluminium 
salts  by  the  addition  of  a  slight  excess  of  ammonium  hydroxide. 
As  several  other  substances  are  also  thrown  down  by  ammonium 
hydroxide  in  a  form  which  often  resembles  the  aluminium  pre- 
cipitate,   the   following   additional   test   should   be   made.     The 
precipitate,  collected  on  a  filter,  is  washed  with  water,  and  after 
removing  it  to  a  test-tube,  is  warmed  with  a  few  cc.  of  a  solution 
of  potassium  hydroxide.  Aluminium  hydroxide,  if  present,  will  dis- 
solve easily  and  may  be  filtered  away  from  the  other  substances, 
except  beryllium,   that  may   have   precipitated.     The  presence 

22 


SIMPLE  TESTS  FOR  THE  ELEMENTS  23 

of  aluminium  is  proved  by  adding  ammonium  hydroxide  to  the 
filtrate,  after  it  has  been  acidified  with  hydrochloric  acid.  The 
reprecipitated  aluminium  hydroxide  may  be  further  tested  by 
igniting  it  on  charcoal,  after  moistening  it  with  cobalt  nitrate. 

To  detect  aluminium  in  insoluble  silicates,  where  the  above 
methods  cannot  be  directly  applied,  see  page  59. 

Antimony,  Sb— 120.2 

1.  Flame    Test. — Antimony  compounds  when  heated  in  the 
R.F.  impart  a  pale  greenish  color  to  the  flame,  owing  to  the 
volatilization  of  metallic  antimony.     (Care  should  be  taken  not 
to  alloy  the  platinum  forceps  when  heating  antimony  or  its  com- 
pounds.) 

2.  Heating  on  Charcoal. — Antimony  and  its  compounds,  with 
the  exception  of  a  few  oxides,  yield,  when  heated  in  the  O.F.,  a 
dense  white  sublimate  of  oxide  of  antimony,  which  deposits  at  a 
short  distance  from  the  assay  and  has  a  bluish  appearance  on  its 
edges.     It  is  completely  volatile  in  both  the  O.F.  and  R.F.,  and  has 
no  distinctive  odor. 

When  soda  is  used  as  flux  with  antimony  minerals,  small 
gray,  metallic  globules  of  antimony  are  sometimes  obtained  in  the 
R.F.  They  are  brittle. 

In  the  presence  of  other  elements,  which  also  yield  sublimates 
on  charcoal,  the  coating  is  not  decisive,  and  confirmatory  tests 
must  be  made,  preferably  the  open  tube  test.  Especial  care 
should  be  taken  not  to  mistake  the  coating  which  is  formed  when 
galena,  PbS,  is  heated  rapidly  on  charcoal  B.B.,  for  that  of 
antimony.  This  coating  is  in  part  due  to  some  combination  of 
PbO  and  SC>2  and  is  apt  to  deceive  beginners.  When  heated 
very  slowly  in  the  O.F.  galena  does  not  give  this  coating.  See 
lead,  p.  44. 

For  a  few  compounds  of  antimony  which  are  not  volatile, 
the  R.F.  must  be  used  first  to  reduce  the  antimony  before  vola- 
tilization can  take  place. 

3.  Iodine   Test  on  the  Plaster   Tablet. — The  antimony  subli- 


24  DETERMINATIVE  MINERALOGY 

mate,  collected  on  a  plaster  tablet,  if  moistened  with  a  drop  of 
hydriodic  acid  and  heated  gently  B.B.,  assumes  an  orange  color 
mixed  with  peach-red.  The  same  result  may  be  obtained  by 
fusing  the  mineral  with  a  flux  composed  of  equal  parts  KI  and  S. 
On  charcoal  the  iodide  coating  is  a  faint  yellow. 

4.  Test  in   the   Open    Tube. — Antimony  and  its  compoundr, 
with  the  exception  of  a  few  oxides,  when  heated  in  the  open  tube 
yield  a  white  sublimate  of  antimony  oxide  or  oxides. 

When  sulphur  is  present,  the  sublimate  usually  tr,kes  the  form 
of  a  dense  white  smoke,  the  greater  part  of  which  settles  along 
the  under  side  of  the  tube,  while  a  part  deposits  as  a  white  ring 
not  far  from  the  heated  part.  The  ring,  when  examined  with  a 
lens,  is  often  found  to  consist  of  two  forms  (octahedrons  and  prisms) 
of  crystallized  antimony  trioxide,  Sb20s.  It  is  volatile  and  can 
be  slowly  driven  out  completely.  (Compare  arsenic,  p.  25.)  The 
dense  white  sublimate  on  the  under  side  of  the  tube  has  the 
composition  Sb2O4,  is  non-volatile,  infusible,  and  becomes  yellow 
when  heated,  but  turns  white  again  on  cooling.  The  sulphur, 
when  present,  in  some  way  causes  the  formation  of  the  oxide, 
Sb2O4,  along  with  Sb2Os.  Metallic  antimony,  and  a  few  minerals 
containing  sulphur,  yield  the  trioxide  alone. 

5.  Closed  Tube  Test. — Sulphide  of  antimony,  and  many  com- 
pounds containing  antimony  and  sulphur,  when  heated  intensely 
in  the  closed  tube,  yield  a  sublimate,  which  is  black  when  hot, 
but  is  red  or  reddish-brown  when  cold.     It  is  the  oxy sulphide  of 
antimony,  Sb2S2O,  and  its  formation  is  one  of  the  few  closed- 
tube  reactions  in  which  the  small  amount  of  oxygen  in  the  tube 
plays  an  important  part. 

Metallic  antimony  is  not  volatile  when  heated  in  the  closed 
tube,  except  at  a  very  high  temperature,  viz.,  that  at  which  hard 
glass  melts.  This  difference  in  behavior  from  that  of  metallic 
arsenic  (see  p.  25),  which  is  easily  volatile,  should  noted. 

6.  Oxidation  with  Nitric  Acid. — Nitric  acid  oxidizes  antimony 
and   its  compounds,  forming  a  white  cm-ny -^"nd,  metantimonic 
acid,  SbO2OH(?).     This  is  very  ^rsoluble  in  nitric  acid  and  water, 
and  when  filtered  from  the  solution  after  the  latter  has  been 


SIMPLE  TESTS  FO^  THE  ELEMENTS  25 

diluted  with  water,  gives  a  fairly  good  separation  of  antimony 
from  elements  which  are  often  associated  with  it,  especially  from 
small  quantities  of  arsenic.  The  material  on  the  filter  paper 
may  then  be  examined  B.B.  on  charcoal  for  antimony. 

Arsenic,  As — 75 
A.     TESTS  FOR  ARSENIC  IN  MINERALS  CONTAINING  NO  OXYGEN. 

1.  Flame   Test. — When  arsenic  minerals  are  heated  B.B.  in 
the  R.F.  the  arsenic  is  volatilized,  and  imparts  a  pale  violet  color 
to  the  flame. 

2.  Roasting   on   Charcoal. — Arsenic,    or   its   compounds   with 
sulphur  and  the  metals,  when  heated  on  charcoal  in  the  O.F. 
form  volatile   products,  which  oxidize  to  arsenic  trioxide,  As203, 
and  deposit  on  the  charcoal  at  a  considerable  distance  (compare 
antimony)  from  the  assay  as  a  white  and  extremely  volatile  subli- 
mate.    When  the  R.F.  is  used  a  disagreeable  garlic-like  odor  is 
usually  obtained  from  the  fumes  which  are  given  off.     This  odor 
is  very  characteristic,  and  a  minute  quantity  of  arsenic  may  be 
detected  by  means  of  it.     The  odor  is  probably  due  to  the  pres- 
ence of  finely  divided  particles  of  arsenic. 

3.  Roasting  in  the  Open  Tube. — When  arsenic,  or  one  of  its 
compounds  with  sulphur  or  the  metals,  is  heated  very  slowly  in 
the  open  tube,  a  white  crystalline  sublimate  of  arsenic  trioxide, 
As2Os,  is  obtained  in  the  form  of  a  ring  on  the  sides  of  the  tube. 
The  sublimate  is  very  volatile,  and  can  be  entirely  driven  out  of 
the  tube  with  heat  (compare  antimony).     The  fumes  of  AsoOs 
have  no  odor.     On  examining  the  sublimate  with  a  lens  it  will  be 
found  to  consist  of  octahedral  crystals,  which  are  occasionally 
twinned. 

Some  arsenides,  like  arsenopyrite,  FeAsS,  which  gives  off  its 
arsenic  readily,  if  heated  otherwise  than  very  slowly,  yield,  with 
the  white  oxide,  a  yellow  sublimate  of  sulphide  of  arsenic,  or  a 
black  one  of  arsenic.  This  is  because  the  amount  of  oxygen  is 
insufficient  to  completely  oxidize  the  rapidly  volatilizing  arsenic. 


26  DETERMINATIVE  MINERALOGY 

4.  Heating  in  the  Closed  Tube. — Arsenic  is  completely  volatil- 
ized when  heated  in  the  closed  tube,  and  deposits  on  the  walls 
of  the  tube.     A  small  amount  appears  as  a  brilliant  black  ring 
while  a  larger  amount  appears  gray  and  crystalline  in  the  part 
of  the  ring  nearest  the  heated  end.       Some  arsenides  are  de- 
composed in  the  closed  tube,  and  give  this  same  mirror. 

If  the  tube  is  broken  just  below  the  sublimate,  and  heated  so 
that  the  arsenic  is  volatilized,  the  garlic  odor  may  be  obtained, 
which  will  distinguish  it  from  other  black  sublimates. 

5.  Special    Test  for   Oxide   of  Arsenic. — Where   antimony   is 
present  with  a  little  arsenic  in  a  mineral  it   may  be  impossible 
to  tell  surely  from  the  sublimate  obtained  on  charcoal,  or  in  the 
O.T.,  whether  arsenic  is  present  or  not.     In  such  case  the  arsenic 
may  be  detected  by  putting  the  oxides  obtained  in  the  O.T.,  or  on 
charcoal,  in  the  bottom  of  a  closed  tube,  with  a  splinter  of  char- 
coal just  above  it.     (It  is  well  to  draw  the  closed  end  of  the  tube 
out  somewhat  smaller  than  usual.)     Heat  the  splinter  until  it 
becomes  red  hot,  and  then  slowly  heat  the  oxide,  which  is  volatil- 
ized, and  in  passing  over  the  coal  is  reduced,  and  deposits  as  an 
arsenical  mirror  beyond  the  splinter.     This  test  is  an  exceedingly 
delicate  one. 

6.  Oxidation    with    Nitric    Acid. — Concentrated    nitric    acid 
oxidizes   and   dissolves   most   arsenides   with   the   formation   of 
arsenic  acid,  HsAsCX,  which  may  be  detected  by  the  methods 
given  under  B,  §  3. 

B.     DETECTION   OF  ARSENIC   IN    MINERALS  CONTAINING  OXY- 
GEN (THE  NATURAL  ARSENATES). 

1.  Heating  in  the  R.F.  on  Charcoal. — By  intense  ignition  B.B. 
in  the  R.F.  the  arsenates  are  reduced,  yielding  arsenic,  which 
usually  gives  the   characteristic  garlic  odor,  and  yields  a  subli- 
mate of  As2Os  on  the  charcoal. 

2.  (a)  Reduction   in   the   Closed    Tube. — All  fusible  arsenates 
may  be  tested  as  follows :  Put  a  fragment  or  two  of  the  mineral 
in  a  small  closed  tube  with  a  few  splinters  of  charcoal,  and  heat 


SIMPLE  TESTS  FOR  THE  ELEMENTS  27 

intensely  B.B.,  when  the  arsenate  will  be  reduced  and  an  arsen- 
ical ring  or  mirror  formed.  The  mirror  may  be  tested  by 
breaking  the  tube  below  it,  and  noting  the  garlic  odor  when  it  is 
heated. 

(6)  If  the  arsenate  is  infusible  (which  is  seldom  the  case), 
and  easily  reducible  metals,  like  copper,  lead,  and  iron  are  absent, 
the  powdered  mineral  should  be  mixed  with  about  four  volumes 
of  dried  sodium  carbonate  and  a  little  charcoal  dust,  and  heated 
gradually  B.B.  to  an  intense  heat.  Reduction  will  take  place 
and  an  arsenic  mirror  will  be  formed. 

(3)  Precipitation  as  Ammonium  Magnesium  Arsenate. — If  it 
is  found  that  the  above  tests  cannot  be  used,  the  following  test 
in  the  wet  way  may  be  made:  Fuse  the  powdered  mineral  with 
about  six  volumes  of  sodium  carbonate  on  charcoal  in  the  O.F. 
Soak  out  the  sodium  arsenate  thus  formed,  in  a  test  tube,  by 
boiling  for  a  minute  with  water,  filter,  acidify  the  filtrate  with  an 
excess  of  hydrochloric  acid,  then  add  an  excess  of  ammonia  (this 
may  cause  the  precipitation  of  a  little  arsenate)  and  then  a  little 
magnesium  sulphate.  The  arsenic,  if  present,  will  be  precipi- 
tated as  ammonium  magnesium  arsenate,  NEUMgAsC^.  This 
may  be  dried  and  tested  as  directed  under  (26).  In  case  of  a 
very  small  amount  of  precipitate,  the  filter  paper  may  be  charred 
by  gentle  ignition  in  a  porcelain  crucible,  and  the  residue  tested 
as  above. 

Barium,  Ba— 137.4 

1.  Flame    Test. — Barium  minerals,   with  the  exception  of  a 
few   rare   silicates,    impart   a    yellowish-green    coloration   to   the 
flame.     The  color  should  not  be  confused  with  that  yielded  by 
boron    or     phosphorus.     The     flame    may    be     advantageously 
examined  with  the  spectroscope. 

2.  Alkaline  Reaction. — Like  other  minerals  containing  alkali 
or  alkali  earth  metals,  those  of  barium,  with  the  exception  of  the 
silicates  and  phosphates,  give  an  alkaline  reaction  when  placed 
on  moistened  litmus  or  turmeric  paper,  after  being  strongly  ignited 
B.B. 


28  DETERMINATIVE  MINERALOGY 

3.  Precipitation  as  Barium  Sulphate. — Barium  is  completely 
precipitated  from  solutions  of  its  salts,  by  the  addition  of  sul- 
phuric acid,  as  a  white,  heavy  precipitate  of  barium  sulphate, 
BaSC>4.  Insoluble  minerals  must  first  be  fused  with  about 
five  volumes  of  sodium  carbonate,  and,  aftei*  the  sodium  sul- 
phate thus  formed  has  been  thoroughly  leached  out  by  treat- 
ment with  hot  water,  the  barium  carbonate  may  be  dissolved  in 
hydrochloric  acid  and  the  sulphate  test  applied.  The  precipi- 
tated sulphate  may  be  collected  on  a  filter,  washed,  and  tested 
for  the  flame  color  by  introducing  a  little  of  it  on  a  platinum  wire 
into  the  Bunsen  flame. 

Beryllium,  Be— 9.1 

Beryllium,  sometimes  called  glucinium,  Gl,  is  a  compara- 
tively rare  element,  occurring  in  only  a  few  minerals,  the  most 
common  one  being  the  silicate  of  beryllium  and  aluminium, 
beryl.  There  are  no  satisfactory  blowpipe  tests  for  the  element, 
and  it  must  be  tested  for  by  wet  methods.  The  followirg  tests, 
if  executed  carefully,  will  be  found  adequate  for  testing  beryllium 
minerals.  If  a  silicate,  the  mineral  must  be  decompcsed  by 
fusion  with  sodium  carbonate,  preferably  in  a  small  platinum  or 
porcelain  capsule.  The  fusion  is  treated  to  remove  silica,  as 
directed  on  p.  58.  Ammonia  is  added  to  the  filtrate  from  the 
silica,  and  the  resulting  precipitate,  which  resembles  aluminium 
hydroxide  in  appearance,  is  washed  thoroughly  with  water. 
The  precipitate  and  filter  are  warmed  in  a  small  beaker  with 
hydrochloric  acid  and  filtered  into  a  small  casserole  to  remove 
the  paper.  The  solution  is  evaporated  to  a  volume  of  two  or 
three  drops,  cooled,  a  few  drops  of  water  are  added  to  effect 
complete  solution,  and  then  a  little  potassium  hydroxide  solu- 
tion is  added,  a  few  drops  at  a  time,  until  the  precipitate  of  beryl- 
lium hydroxide,  which  forms,  is  just  dissolved.  The  solution  is 
then  diluted  with  50  to  100  cc.  of  cold  water,  any  precipitate 
of  ferric  hydroxide  is  filtered  off,  and  the  liquid  boiled  for  a  short 
time.  If  beryllium  is  present  it  will  now  precipitate  as  the  hydrox- 
ide (aluminium  remains  dissolved). 


SIMPLE  TESTS  FOR  THE  ELEMENTS  29 

If  a  phosphate  is  to  be  tested,  it  must  be  dissolved  in  a  few  cc. 
of  hydrochloric  acid  (after  fusion  with  sodium  carbonate,  if 
insoluble).  Ammonia  is  then  added  to  the  cold  solution  until  a 
permanent  precipitate  forms.  This  is  then  just  redissolved  by 
adding  hydrochloric  acid,  very  cautiously,  a  drop  at  a  time.  To 
this  neutral  solution,  which  should  be  cold,  sodium  acetate  is 
added.  Beryllium  phosphate  is  precipitated,  and  is  filtered  and 
washed.  As  this  may  be  mixed  with  calcium  and  aluminium 
phosphate,  the  precipitate  is  ignited  in  a  crucible  to  burn  off  the 
paper,  and  fused  in  platinum  with  sodium  carbonate.  The 
sodium  phosphate  formed  is  soaked  out  with  hot  water,  and 
removed  from  the  beryllium  oxide  by  filtration  and  washing. 
The  beryllium  is  then  dissolved  in  hydrochloric  acid,  and  treated 
with  potassium  hydroxide,  as  described  in  the  paragraph  above. 

If  beryllium  hydroxide  is  ignited  on  charcoal  with  cobalt 
nitrate  solution  a  lavender  color  is  said  to  result. 

Bismuth,  Bi— 208 

1.  Reduction  to  Metallic  Bismuth  on  Charcoal,  and  the  Forma- 
tion of  a  Coating  of  Bismuth  Oxide. — Globules  of  metallic  bismuth 
may  be  obtained  if  the  finely  powdered  bismuth  mineral  is  mixed 
with  about  three  volumes  of  sodium  carbonate  and  heated  B.B. 
in  the  R.F.     The  globules  are  bright  while  in  the  R.F.,  but 
quickly  tarnish  to  a  dull  gray  on  exposure  to  the  air.     When 
cold  they  are  rather  brittle  and  break  to  pieces  when  hammered, 
instead  of  flattening  to  a  thin  sheet,  like  lead.     B.B.  bismuth  is 
somewhat  volatile.     In  this  state  it  unites  with  oxygen  from  the 
air,  forms  bismuth  oxide,  Bi2Oa,  which  deposits  on  the  charcoal 
near  the  assay  as  a  deep  orange-yellow  coating  when  hot,  fading 
to  a  lighter  shade  on  cooling.     The  oxide  is  volatile  in  both  the 
O.F.  and  R.F.     The  coatings  of  lead  and  bismuth  oxides  are 
quite  similar,  but  may  be  distinguished  by  the  iodine  test  (§2, 
below). 

2.  Iodine  Test. — The  coating  of  oxide,  obtained  as  above,  is 
moistened  with  a  drop  or  two  of  hydriodic  acid  and  heated  gently 


30  DETERMINATIVE  MINERALOGY 

with  a  small  O.F.  A  coating  will  be  formed  which  is  yellow 
near  the  assay,  but  bordered  on  the  outer  edges  with  red  or 
brownish-red.  The  same  result  may  be  obtained  by  heating 
gently,  with  a  small  oxidizing  flame,  a  small  amount  of  the  mineral 
with  three  or  four  volumes  of  a  mixture  of  equal  parts,  potassium 
iodide  and  sulphur.1 

If  a  plaster  tablet  (see  page  12)  is  used  instead  of  charcoal,  a 
chocolate-brown  coating  of  bismuth  iodide  is  obtained,  which 
turns  to  a  brilliant  red  if  held  in  the  fumes  of  strong  ammonia 
for  a  short  time. 

3.  Wet  Tests. — The  hydrochloric  acid  solution  of  the  mineral 
is  evaporated  until  only  a  few  drops  remain.  These  are  poured 
into  a  test-tube  half  full  of  cold  water,  when  a  white  precipitate 
of  bismuth  oxy chloride  is  formed.  This  may  be  filtered  off  and 
tested  B.B.  on  charcoal.  If  the  mineral  is  insoluble  in  hydro- 
chloric acid,  the  nitric  acid  solution  may  be  evaporated  with  an 
excess  of  hydrochloric  acid,  until  no  nitric  acid  remains. 

Lead  may  be  separated  from  the  bismuth  as  follows:  Dissolve 
in  cone,  nitric  acid,  cool,  add  2  or  3  cc.  of  concentrated  sul- 
phuric acid,  and  evaporate  until  the  nitric  acid  is  expelled  and 
dense  white  fumes  of  sulphuric  acid  appear.  Cool  and  pour 
into  10  cc.  of  water,  rinsing  out  the  tube  or  dish  with  a  little 
cold  water.  Stir  and  allow  to  stand  for  five  minutes.  Filter  off 
the  precipitated  lead  sulphate,  which  may  be  tested  on  charcoal 
B.B.  by  3,  p.  45.  To  the  filtrate  add  6N  •  NH4OH  in  excess,  which 
will  precipitate  Bi(OH)3,  if  any  bismuth  is  present.  Filter,  and 
dissolve  the  precipitate  in  HC1.  Concentrate  this  solution,  and 
pour  into  a  large  amount  (100  cc.)  of  water;  a  white  precipi- 
tate of  BiOCl  will  indicate  bismuth.  This  precipitate  may  be 
further  tested  by  collecting  on  a  filter  and  pouring  on  it  a  solution 
of  freshly  prepared  sodium  stannite.  If  the  precipitate  was  BiOCl, 
a  black  residue  of  metallic  bismuth  will  be  formed.  The  sodium 
stannite  is  prepared  by  taking  a  few  drops  of  SnCl2,  diluting  with 
5  cc.  of  water  and  adding  NaOH  solution,  a  few  drops  at  a  time, 

1  This  mixture  is  known  as  "  Bismuth  Flux." 


SIMPLE  TESTS  FOR  THE  ELEMENTS  31 

until  the  precipitate  of   Sn(OH)2,  which  forms  first,  just  redis- 
solves. 

Boron,  B — 11 

1.  Flame    Test. — Many   boron   minerals   when  heated   alone 
B.B.   impart  a  bright  green  color  to  the  flame.  The  green  is 
inclined  somewhat  to  yellow   (siskin  green),  and  must  not  be 
confused  with  the  green  of  barium  and  phosphorus. 

Minerals  which  do  not  give  the  boron  flame  directly  may  be 
mixed  with  about  three  volumes  of  a  mixture  of  equal  parts 
calcium  fluoride  (fluorite)  and  acid  potassium  sulphate,  and 
introduced  into  the  Bunsen  flame  on  a  platinum  wire.  A  green 
flame,  of  momentary  duration,  will  be  seen  if  boron  is  present. 
In  this  reaction  the  calcium  fluoride,  CaF2,  and  the  acid  potas- 
sium sulphate,  HKSO4,  react  to  form  hydrofluoric  acid,  HF, 
which  attacks  the  mineral,  forming  the  fluoride  of  boron,  BFs, 
which  is  a  very  volatile  salt  of  boron,  and  gives  the  characteristic 
flame  coloration. 

2.  Turmeric-paper  Test. — A  piece  of  turmeric  paper  is  moist- 
ened in  a  dilute  hydrochloric  acid  solution  of  the  mineral  to  be 
tested,  and  dried  at  100°  C.  on  the  outside  of  the  test-tube  con- 
taining the  boiling  solution.     If  boron  is  present  the  paper  assumes 
a  reddish-brown  color,  which  is  changed  to  an    inky-black  by 
moistening  with  ammonia.     This  is  a  very  delicate  test.     If  the 
mineral  is  insoluble  in  acids  it  must  be  first  fused  with  sodium 
carbonate,  as  directed  on  p.  14,  and  then  dissolved. 

Bromine,  Br— 79.9 

When  a  bromide  is  heated  in  a  large  closed  or  bulb  tube  with 
acid  potassium  sulphate  and  pyrolusite  (manganese  dioxide,) 
bromine  is  liberated  as  a  red  vapor,  which  condenses  to  a 
red  liquid  if  much  is  present.  Iodine  and  chlorine  are  liberated 
from  iodides  and  chlorides  respectively  in  the  same  way,  so  that 
in  order  to  distinguish  these  elements  surely  in  the  presence  of 
each  other,  more  elaborate  wet  methods  must  be  used.  For 


32  DETERMINATIVE  MINERALOGY 

these,  the  student  is  referred  to  Brush  and  Penfield's  "  Determina- 
tive Mineralogy/'  etc.,  page  69,  or  to  works  on  qualitative  analysis. 
Silver  bromide,  which  is  the  only  important  compound  of 
bromine  found  as  a  mineral,  if  heated  in  a  closed  tube  with  galena, 
PbS,  yields  a  sublimate  of  lead  bromide,  PbBr.  This  is  sulphur 
yellow  when  hot  and  white  when  cold.  Iodide  of  silver,  if  present, 
as  it  often  is  in  nature,  may  lead  to  confusion.  (See  reference 
given  above  for  wet  tests.) 

Cadmium,  Cd— 112.4 

Cadmium  minerals  when  heated  B.B.  in  the  R.F.,  after  mix- 
ing with  sodium  carbonate,  yield  a  reddish-brown  coating  of 
cadmium  oxide,  which  is  yellowish,  distant  from  the  assay.  It 
is  usually  iridescent  if  only  a  little  forms.  As  cadmium  occurs  in 
certain  zinc  minerals,  this  coating  may  be  noticed  just  before  the 
zinc  oxide  begins  to  deposit  when  such  minerals  are  heated  B.B. 
It  is,  however,  best  to  test  for  cadmium  by  the  regular  wet  analyt- 
ical methods.  It  may  be  separated  from  zinc  by  precipitating  it, 
as  the  yellow  sulphide,  with  hydrogen  sulphide  in  a  cold  solution 
of  its  sulphate  which  has  present,  beside  a  little  free  sulphuric, 
about  10  cc.  of  dilute  hydrochloric  acid,  in  a  final  volume  of  about 
100  cc. 

Calcium,  Ca— 40 

1.  Flame   Test. — Some  calcium  minerals  impart  a  yellowish- 
red  color  to  the  flame.     This  flame  is  much  stronger  if  the  frag- 
ment or  powder  is  moistened  with  hydrochloric  acid.     In  neither 
case  is  the  test  sufficiently   characteristic  to  be  decisive,   and 
spectroscopic  or  other  confirmatory  tests  must  be  made.     The 
flame  must  not  be  mistaken  for  that  of  strontium,  which  has  a 
brilliant  crimson  color.     It  should  be  remarked,  that  if  a  little 
sodium  is  present  on  the  mineral  specimen,  a  strontium  flame 
may  appear  yellowish  and  be  mistaken  for  that  of  calcium. 

2.  Alkaline  Reaction  on  Test  Paper. — With  the  exception  of 
the  silicates,  phosphates,  borates,  and  the  salts  of  a  few  rare  acids, 


SIMPLE  TESTS  FOR  THE  ELEMENTS  33 

calcium  minerals  give  an  alkaline  reaction  when  placed  on  moist- 
ened turmeric  or  litmus  paper  after  strong  ignition  B.B. 

3.  Precipitation  as  Calcium  Sulphate. — Calcium  forms  a  sul- 
phate which  is  sparingly  soluble  in  water  and  hydrochloric  acid. 
Accordingly,  this  sulphate  may  be  thrown  down  from  not  too 
dilute,  nor  too  strongly  acid  solutions,  by  the  addition  of  sulphuric 
acid,  and,  if  carried  out  as  directed  beyond,  is  a  very  character- 
istic test.     The  solution  to  be  tested  should  be  freed,  by  evapora- 
tion if  necessary,  of  all  but  a  very  little  free  hydrochloric  or  nitric 
acid,  and  should  contain  only  enough  water  to  keep  the  salts 
entirely  in  solution.     A  few  drops  of  dilute  sulphuric  acid  will 
produce  in  such  a  solution,  if  calcium  is  present,  a  white,  feathery 
precipitate  of  the  hydrated  calcium  sulphate,  CaSO4-2H2O.     If 
much  calcium  is  present  it  will  be  thick  and  curdy.     This  pre- 
cipitate may  be  readily  dissolved  upon  the  addition  of  water, 
and    warming,    and    this    behavior    distinguishes    calcium   from 
barium  and  strontium  sulphates.     If  the  solution  in  which  cal- 
cium is  to  be  tested  for  is  divided  into  two  parts,  and  one  diluted 
with  about  ten  volumes  of  water,  it  will  be  found,  that  upon  the 
addition  of  sulphuric  acid  to  both,  a  precipitate  will  form  only 
in  the  portion  which  was  not  diluted. 

4.  Behavior    with    Ammonia. — Calcium    is    not    precipitated 
from  its  solutions  by  ammonium  hydroxide,  except  when  acids 
are  present  which  form  with  calcium,  under  such  conditions,  an 
insoluble  compound.     The  most  important  of  these  acids  with 
which  calcium  is  commonly  found  in  nature  are  carbonic,  phos- 
phoric, silicic,  and  boric  acids.     This  important  behavior  should 
be  carefully  borne  in  mind  while  testing  solutions  of  minerals  with 
ammonia.     Carbonic  acid  is  quickly  removed  from  the  solution 
by  boiling,  so  that  no  precipitate  is  formed  in  boiled  solutions 
obtained  from  carbonates,  and  test  §  5  or  §  6  may  be  used;  when 
the  other  acids  are  present,  §  3  may  be  used. 

5.  Precipitation  as  Ammonium  Oxalate. — Ammonium  oxalate 
produces  in  alkaline  and  even  slightly  acid  solutions  of  calcium 
salts  a  complete  precipitation  of  calcium  as  the  oxalate,  CaC2C>4. 
If  it  is  desired  to  remove  the  precipitate  from  the  solution,  it  will 


34  DETERMINATIVE  MINERALOGY 

be  found  best  to  make  the  precipitation  in  a  boiling  hot  solution, 
and  to  continue  the  boiling  for  a  minute  or  so,  before  any  attempt 
is  made  to  filter  it. 

6.  For  the  detection  of  calcium  in  silicates  and  other  complex 
minerals,  see  page  58,  §  4. 

Carbon,  C — 12 

A.  1.  Bituminous  Coals,    Hydrocarbons,  and  Organic  Matter. 
Closed  Tube  Reactions. — If  the  above  substances  are  heated  in 
the  closed  tube,  tarry  matters,  oils,  gases,  and  water  are  given  off 
and  distill  up  the  tube.     A  peculiar  "  empyreumatic  "  odor  is 
usually  observed.     If  the  tube  is  drawn  out  to  a  capillary  at  the 
open  end,  the  more  volatile  products  of  the  distillation  may  be 
lighted  with  a  match.     The  residue  is  usually  nearly  pure  carbon. 

2.  Anthracite  Coals  and  Graphite. — These  two  forms  of  carbon 
yield  little  or  no  volatile  matter  when  heated  in  the  closed 
tube.  They  may,  however,  be  tested  in  the  closed  tube  as  follows : 
Put  a  number  of  splinters  of  pyrolusite,  manganese  dioxide,  in 
the  bottom  of  a  closed  tube  (a  bulb  tube  is  better  if  at  hand) 
and  above  it  a  small  piece  of  the  material  to  be  tested.  Heat 
the  substance  to  redness,  at  the  same  time  heating  the  pyrolusite. 
The  latter  will  give  off  oxygen,  which  will  cause  the  fragment  to 
burn  if  it  consists  of  carbon. 

B.  1.  Carbonates;    Effervescence    with    Acids. — Carbonic    acid 
is  liberated  when  a  carbonate  is  dissolved  in  one  of  the  strong 
mineral  acids  (HC1,  HNOs,  H^SCU),  and  as  it  breaks  down  into 
water  and  carbon  dioxide  (H2COs  =  H2O+CO2)  the  latter  escapes 
from  the  solution  with  bubbling  (effervescence).     It  is  best  to  use 
dilute  acids,  since  concentrated  ones  sometimes  prevent  or  hinder 
solution  (with  cerussite,  PbCOs,  for  example).     Although  some 
carbonates  effervesce  in  cold  acids,  many  require  the  application 
of  heat  to  effect  solution,  so  that  in  testing  a  carbonate,  the  solu- 
tion should  always  be  heated  if  it  does  not  effervesce  when  cold. 

When  heating  is  resorted  to,  care  should  be  taken  not  to 
mistake  the  escape  of  steam  bubbles  during  boiling  for  efferves- 
cence. 


SIMPLE  TESTS  FOR  THE  ELEMENTS  35 

Calcite  and  aragonite  (CaCOs)  effervesce  freely  in  very 
dilute  HC1  or  HNOa,  or  in  the  weaker  acids,  acetic  and  citric, 
and  this  fact  serves  as  a  ready  means  of  distinguishing  these 
minerals  from  other  common  ones. 

Since  carbon  dioxide  is  a  colorless,  odorless  gas  it  is  easily 
distinguished  from  the  other  gases,  H^S,  Cl,  NO2,  which  may  be 
encountered  in  testing  minerals.  Carbon  dioxide  may  be  identified 
by  pouring  the  heavy  gas,  which  has  collected  in  the  test-tube,  into 
another  tube  containing  a  few  cc.  of  a  solution  of  barium  hydroxide. 
The  tube  is  then  closed  with  the  thumb  and  shaken,  when,  if  CO2 
is  present,  a  white  precipitate  of  barium  carbonate  will  form. 

2.  Decomposition  in  the  Closed  Tube. — Most  carbonates  are 
decomposed  by  heating  in  the  closed  tube  with  the  evolution 
of  carbon  dioxide.  Some  are  decomposed  easily,  like  iron  car- 
bonate; others,  like  calcium  carbonate,  require  a  rather  high 
temperature.  By  introducing  a  drop  of  barium  hydroxide  solu- 
tion into  the  mouth  of  the  tube  with  a  pipette  the  presence  of 
carbon  dioxide  will  be  indicated  by  the  formation  of  a  white  pre- 
cipitate of  barium  carbonate. 

Cerium,  Ce— 140.2  (see  under  Rare  Earths) 
Chlorine,  Cl— 35.5 

1.  Precipitation  as  Silver  Chloride. — Silver  nitrate,  added  to 
the  aqueous  or  nitric  acid  solution  of  a  chloride,  produces  a 
precipitate  of  silver  chloride,  AgCl.  If  only  a  little  of  the  chloride 
is  present  the  silver  nitrate  causes  only  an  opalescent  turbidity; 
if  more,  the  precipitate  is  white  and  curdy.  On  exposure  to  the 
light  it  turns  purple.  Bromine  and  iodine  likewise  form  precipi- 
tates with  silver  nitrate.  For  methods  dealing  with  the  separa- 
tion of  these  elements,  see  Brush  and  Penfield's  "  Blowpipe 
Analysis,"  page  69,  or  standard  works  in  analytical  chemistry. 

Where  the  mineral  containing  the  chloride  is  insoluble,  it 
must  first  be  fused  with  sodium  carbonate,  the  fusion  soaked  out 
with  water,  acidified  with  nitric  acid,  filtered  if  necessary,  and 
silver  nitrate  then  added. 


36 


DETERMINATIVE  MINERALOGY 


2.  Evolution  of  Chlorine. — If  the  powdered  chloride  is  mixed 
with  about  four  volumes  of  potassium  bisulphate  and  a  little 
pyrolusite  (manganese  dioxide),  and  heated  in  a  small  test-tube, 
or  better,  a  bulb  tube,  chlorine  gas  will  be  given  off.  This  may 
be  recognized  by  its  pungent  odor  and  the  fact  that  it  will  bleach 
a  piece  of  litmus  paper  held  in  the  end  of  the  tube. 

Insoluble  chlorides  must  first  be  fused  with  sodium  carbonate, 
the  fusion  pulverized,  and  then  treated  as  above. 

Chromium,  Cr — £2.0 

1.  Bead  Tests. — The  bead  tests  are  very  characteristic  and 
afford  a  satisfactory  method  of  detecting  chromium  in  its  minerals. 
The  intensity  of  the  various  colors  given  in  the  accompanying 
table  depends  on  the  relative  amount  of  powder  used,  but  the 
colors  are  distinctive  even  when  very  little  material  is  used. 


Oxidizing 
Flame 

SALT  OF  PHOSPHORUS 

BORAX 

g 

w 

Dirty  Green 

Decided  Yellow 

o 
O 

Fine  Green 

Fine  Yellowish-Green 

Reducing 
Flame 

1 

Same  as  in  O.F. 

Fine  Green 

o 
O 

Same  as  in  O.F. 

Fine  Green 

Where  small  quantities  of  chromium  are  associated  with  other 
substances  which  color  the  fluxes,  the  following  method  is  recom- 
mended : 

2.  Precipitation  as  Lead  Chromate. — If  the  mineral  is  a  silicate 


SIMPLE  TESTS  FOR  THE  ELEMENTS  37 

it  may  be  decomposed  by  fusing  with  a  mixture  of  four  parts 
sodium  carbonate  and  two  of  potassium  nitrate,  in  a  platinum 
spoon  or  crucible.  If  the  mineral  is  an  oxide  and  difficult  to 
decompose,  a  large  borax  bead  may  be  saturated  with  the  mineral, 
and  this  bead  crushed  and  fused  with  two  or  three  volumes  of 
sodium  carbonate  and  one  of  potassium  nitrate.  Where  sodium 
peroxide  is  at  hand,  the  above  decompositions  are  best  made  by 
fusing  with  that  reagent.  Whichever  one  of  these  fluxes  is  used, 
a  soluble  alkali  chromate  is  formed.  This  is  soaked  out  in  about 
5  cc.  of  water,  the  solution  filtered  (the  filtrate  is  yellow  if  chro- 
mium is  present),  slightly  acidified  with  acetic  acid,  filtered  again 
if  necessary,  and  any  chromium  present  thrown  down  as  a  yellow 
precipitate  of  lead  chromate  by  adding  some  lead  acetate  to  the 
solution.  This  precipitate  may  be  collected  on  a  small  filter  and 
tested  in  the  bead  according  to  §  1. 

Cobalt— 58.9 

1.  Bead  Tests. — Oxide  of  cobalt  imparts  a  deep  blue  color  to 
both  the  borax  and    salt    of    phosphorus    beads.     This  is  an 
extremely  delicate  test  and  even  serves  to  identify  small  amounts 
of  cobalt  when  comparatively  large  quantities  of  iron  and  nickel 
are  present. 

WTien  copper  and  nickel  are  present  in  quantity,  and  it  is 
desired  to  test  for  cobalt,  the  borax  bead  may  be  removed  from 
the  wire  and  heated  in  a  strong  R.F.  on  charcoal,  until  copper 
and  nickel  are  reduced  to  the  metallic  state,  when  the  borax  will 
show  the  blue  of  cobalt. 

2.  Nitric  Add  Solutions  of  minerals  which  contain  consider- 
able cobalt  are  colored  rose-red.     The  addition  of  an  excess  of 
ammonia  turns  the  solution  brown.     On  standing  this  becomes 
red. 

3.  Test  for  Cobalt  in  the  Presence  of  Nickel. — Small  amounts 
of  cobalt  in  the  presence  of  nickel  may  be  detected  as  follows: 
To  a  little  of  the  powdered  mineral  in  a  small  test-tube,  a  cubic 
centimeter  of  cone.  HNOs  (1.42  Sp.  G.)  is  added.     After  being 


38  DETERMINATIVE  MINERALOGY 

allowed  to  stand  for  several  minutes,  a  few  drops  are  taken  out 
with  a  pipette  (made  by  drawing  out  a  small  glass  tube)  and 
evaporated  to  dryness  in  a  small  test-tube  or  on  a  watch  glass. 
The  dry  residue  is  taken  up  in  two  or  three  drops  of  6N  •  HC1  and  a 
drop  or  two  of  alpha-nitrosobeta-naphthol  solution  is  added.  A 
flocculent  red  precipitate  slowly  appears  if  cobalt  is  present. 
The  reagent  should  be  made  up  fresh  at  least  once  a  month  by 
dissolving  one-half  gram  of  the  salt  in  15  cc.  of  glacial  acetic  acid, 
diluting  with  an  equal  amount  of  water  and  filtering, 

Copper— 63.6 

1.  Flame   Color. — Copper  oxide   and   some   copper  minerals, 
if  introduced  in  a  finely  divided  form  into  the  clear  flame,  give  an 
emerald-green  color.     Fragments  of  copper  minerals  will  often 
give  this  color  B.B.     The  powder  or  a  fragment  of  a  copper 
mineral,  if  ignited  on  charcoal  B.B.  (in  the  O.F.  if  it  is  a  sulphide 
or  arsenide,  etc.),  moistened  with  hydrochloric  acid  and  again 
ignited,    gives   the   brilliant   azure-blue    flame    color   of   copper 
chloride.     The  blue  is  usually  tinged  with  green,  owing  to  the 
partial  decomposition  of  the  chloride  to  the  oxide.     This  is  a  very 
characteristic  test. 

2.  Reduction  to  Metallic  Copper  on  Charcoal. — Copper  is  easily 
reduced  from  its  oxides,  or  from  minerals  containing  the  oxides, 
when  heated  strongly  on  charcoal,  with  a  flux  in  the  R.F.     With 
a  little  patience  and  continued  heating,  the  reduced  copper  may 
be  collected  into  a  globule.     Since  copper  is  rather  hard  to  fuse 
B.B.,  it  is  best  to  take  a  rather  small  quantity  of  mineral  and  to 
use  about  three  volumes  of  flux,  which  may  be  sodium  carbonate, 
although,  where  metals  not  easily  reduced,  like  iron,  are  present, 
a  mixture  of  equal  parts  sodium  carbonate  and  borax  will  be  found 
to    yield    better    results.     Minerals    containing    volatile    elements 
(S,  As,  Sb)  should  be  carefully  roasted  (see  p.  13)   before  fluxing 
and  reducing.     The  globules,   which  are  covered  with  a  black 
coating  of  oxide,  may  be  easily  recognized  by  their  toughness, 
malleability,  and  their  reddish  color,  when  cut  or  hammered. 


SIMPLE  TESTS  FOR  THE  ELEMENTS  39 

3.  Color   of  Solutions. — Acid    solutions   of   copper   salts   are 
either  green  or  blue-green.     If  an  excess  of  ammonia  is  added  to 
these  a  deep  blue  solution  is  obtained.     Care  should  be  taken  in 
not  confusing  green  solutions  of  nickel  salts  with  those  of  copper, 
or  the  blue  produced  by  ammonia  in  copper  solutions  with  a  very 
similar,  but  fainter,  blue  produced  in  the  same  way  in  nickel 
solutions. 

4.  Bead  Tests. — In  the  O.F.  copper  oxide  colors  the  borax  and 
salt  of  phosphorus  beads  green  when  hot,  and  blue  or  bluish- 
green  when  cold,  due  to  the  presence  of  dissolved  cupric  oxide, 
CuO.     In  the  R.F.,  if  only  a  little  oxide  is  present,  the  colors  are 
paler,  but  if  considerable  is  there,  there  is  a  separation  of  cuprous 
oxide,  Cu2O,  or  even  of  metallic  copper,  which  makes  the  bead 
appear  an  opaque  red  in  reflected  light. 

Perhaps  the  best  way  to  effect  the  reduction  of  copper  in  the 
bead,  especially  if  there  is  only  a  little  present,  is  to  remove  it 
from  the  wire  after  it  has  been  heated  in  the  O.F.,  and  heat  it  in 
the  R.F.  on  charcoal,  with  a  small  granule  of  tin.  The  tin  takes 
oxygen  away  from  the  CuO,  reducing  it  to  Cu2O,  or  copper.  Too 
long  heating  may  cause  the  formation  of  a  copper  globule 

Fluorine,  F— 19 

1.  Test  with  Potassium  Bisulphate.  This  test  is  limited  to 
minerals,  which  contain  considerable  fluorine,  and  are  decomposed 
by  the  bisulphate  reagent. — Mix  the  finely  powdered  mineral  with 
three  or  four  volumes  of  potassium  bisulphate,  and  heat  the 
mixture,  gently  at  first,  in  a  large  closed  tube  (an  open  tube 
sealed  off),  or  much  better,  a  bulb  tube.  Hydrofluoric  acid 
will  be  liberated,  which  reacts  with  the  silica  in  the  glass  of 
the  tube,  etching  this,  and  forming  a  volatile  compound,  silicon 
fluoride,  SiFi,  which  passes  up  the  tube  with  the  water  formed  by 
the  reaction  (SiO2+4HF  =  SiF4  +  2H2O).  In  the  cool  part  of  the 
tube  these  products  react  according  to  the  equation,  3SiF4+2H2O 
=  2H2SiF6+SiO2,  and  deposit  on  the  sides  of  the  tube  as  a  white 
ring.  This  white  ring  is  the  most  characteristic  part  of  the 


40  DETERMINATIVE  MINERALOGY 

reaction,  although  the  etching  on  the  tube  in  the  immediate  neigh- 
borhood of  the  fusion  may  usually  be  seen.  The  ring  is  volatile 
when  heated,  and  may  be  made  to  pass  up  the  tube.  This  is 
because  the  compounds  H^SiFe  and  SiC>2  when  heated  form  SiF4 
and  H2O  again.  To  complete  the  test,  cut  off  the  tube  just  below 
the  ring,  wash  the  inside  of  the  tube  carefully  with  water  to  remove 
the  H2SiF6,  which  is  soluble,  and  then  dry  the  tube  in  the  flame, 
when  a  nonvolatile  white  ring  of  8162  will  remain.  Where  very 
small  amounts  of  substance  are  to  be  tested  it  is  advisable  to  mix 
a  little  powdered  silica  or  glass  with  the  bisulphate,  as  this  ensures 
the  formation  of  the  SiF±  if  fluorine  is  present.  The  above  test 
is  particularly  serviceable  where  small  precipitates  of  calcium 
fluoride,  obtained  as  described  under  §  3,  are  to  be  tested. 

2.  Test  with  Sodium  Metaphosphate. — This  test  can  be  applied 
to  minerals  which  are  not  decomposed  by  the  bisulphate  of  potash, 
provided  not  less  than  5  per  cent  of  fluorine  is  present.     From 
four  to  six  parts  of  sodium  metaphosphate,  NaPOs,  to  one  of  the 
mineral  should  be  used.     Hydrofluoric  acid  is  liberated,  etches 
the  glass,  and  deposits  a  ring  of  silica  as  described  under  §  1.     The 
sodium  metaphosphate  may  be  made  by  fusing   some  salt  of 
phosphorus  in  a  platinum  dish,  or  on  a  loop   of   platinum  wire 
until  the  water  and  ammonia  are  expelled. 

3.  Precipitation  as  Calcium  Fluoride. — This  test  is  especially 
useful  in  detecting  the  presence  of  small  quantities  of  fluorine  in 
silicates.     The  mineral  must  be  first  decomposed  with  sodium 
carbonate,  as  described  under  silica  (p.  58).     The  fusion  is  pulver- 
ized, boiled  in  a  few  cc.  of  water  to  soak  out  the  sodium  fluoride, 
which  has  been  formed  if  fluorine  is  present,  and  filtered.     The 
filtrate  is  acidified  with  hydrochloric  acid,  boiled  to  expel  carbon 
dioxide,  made  strongly  alkaline  with  ammonia,  and  a  little  cal- 
cium chloride  added,  to  precipitate  the  fluorine  as  calcium  fluoride. 
Other  substances  may  be  precipitated  along  with  the  calcium 
fluoride,  so  that  it  is  necessary  to  filter  off  the  precipitate,  wash 
well  with  water,  ignite  the  paper  in  a  crucible,  and  test  the  residue 
according  to  §  1. 

4.  Add  Water  in  the  Closed  Tube. — Some  minerals  containing 


SIMPLE  TESTS  FOR  THE  ELEMENTS  41 

fluorine  and  hydroxyl  yield  acid  water  (due  to  the  presence  of 
HF)  in  the  closed  tube  (tested  with  litmus  paper),  and  some- 
times etch  the  glass.  Unless,  however,  the  etching  is  distinctly 
seen,  the  presence  of  fluorine  must  be  proved  by  one  of  the  other 
tests. 

Germanium,  Ge — 72.5 

This  exceedingly  rare  element  is  only  known  to  occur  in 
the  minerals  argyrodite,  canfieldite,  and  in  small  quantities  in 
euxenite. 

Sublimate  on  Charcoal. — When  argyrodite  is  heated  on  char- 
coal B.B.  germanium  yields  a  white  coating  near  the  assay.  On 
longer  heating  this  moves  further  away,  and  assumes  a  lemon- 
yellow  color  mixed  with  a  greenish  to  brownish  shade;  examined 
with  a  lens  the  coating  appears  glazed,  and  occasional  transparent 
or  white  globules  may  be  seen. 

Gold,  Au— 197.2 

Gold,  when  it  is  not  present  in  the  specimen  in  such  form  that 
it  can  be  recognized  by  its  physical  properties,  is  usually  tested 
for  by  assay  methods.  For  these  methods,  as  adapted  for  blow- 
pipe tests,  see  under  Silver;  also  Brush  and  Penfield's  "  Blowpipe 
Analysis,"  pp.  78-80;  R.  H.  Richard's  "Notes  on  Blowpipe 
Assaying,"  and  Plattner's  "  Blowpipe  Analysis,"  by  Cornwall, 
eighth  edition,  p.  374. 

Metallic  gold  is  fusible  B.B.  on  charcoal  and  does  not  yield  a 
coating  of  oxide.  It  is  insoluble  in  any  single  acid,  but  dissolves 
in  aqua  regia.  Its  yellow  color  and  great  malleability  are  striking 
physical  characteristics. 

Hydrogen,  H — 1 

Hydrogen  occurs  in  many  minerals  in  combination  with 
oxygen,  and  when  such  are  heated,  the  hydrogen,  united  to  the 
oxygen,  is  given  off  in  the  form  of  water.  Testing  for  hydrogen 
amounts,  therefore,  to  testing  for  water;  see  page  73. 


42  DETERMINATIVE  MINERALOGY 


Iodine,  1—126.9 

1.  Closed  Tube  Tests. — Heated  in  the  closed  tube  with  potas- 
sium bisulphate,  with  or  without  manganese  dioxide,  iodides  are 
decomposed,  yielding  a  violet  colored  vapor. 

When  silver  iodide,  which  is  the  only  important  iodine  mineral, 
is  heated  in  the  closed  tube  with  galena,  PbS,  a  sublimate  of  lead 
iodide  is  obtained,  orange-red  when  hot,  lemon-yellow  when  cold. 

Silver  iodide  is  precipitated  by  silver  nitrate,  and  differs  from 
the  bromide  and  chloride  by  not  being  readily  soluble  in  ammonia. 

Iridium  (see  under  Platinum) 
Iron,  Fe— 55.8 

1.  Test  with  the  Magnet. — If  placed  in  the  field  of  a  strong 
electro-magnet,  with  its  poles  close  together  so  as  to  give  a  con- 
centrated   field,    a    great    many    minerals    containing    iron    are 
attracted.     Magnetite  and  pyrrhotite  are  the  only  common  min- 
erals strongly  attracted  by  the  ordinary  magnet,  and  even  pyrrho- 
tite from  some  localities  is  but  feebly  acted  on.     Franklinite,  a 
variety  of  magnetite,  is  somewhat  attracted,  and  many  minerals 
may  be  attracted  because  they  contain  small  grains  of  magnetite. 
Many  minerals  containing  iron  become,  however,  magnetic  after 
heating  B.B.  in  the  R.F.     This  applies  especially  to  the  sulphides, 
oxides,  and  carbonates,  also  to  the  silicates  and  phosphates,  if  the 
content  of  iron  in  them  is  large.     The  silicates,  phosphates,  etc., 
give  a  better  reaction,  however,  if  they  are  fused  in  the  R.F.  with 
about  two  volumes  of  sodium  carbonate,  the  fusion  crushed,  and 
tested  with  a  magnet. 

Always  wait  until  the  fragment  or  powder  which  has  been 
heated  is  cold  before  testing  with  the  magnet.  Even  iron,  when  red 
hot,  is  not  magnetic. 

2.  Tests  for  Ferrous  and  Ferric  Iron. — Soluble  iron  minerals 
may  be  dissolved  in  a  test-tube  with  hot  hydrochloric  or  sulphuric 
acid  without  altering  essentially  the  state  of  oxidation  of  the  iron 


SIMPLE  TESTS  FOR  THE  ELEMENTS  43 

from  that  existing  in  the  original  mineral.  The  resulting  solution 
may  then  be  tested  for  ferrous  and  ferric  iron. 

Ferrous  Iron. — Ferrous  iron  gives  a  deep  blue  precipitate, 
exactly  like  Prussian  blue  in  appearance,  when  potassium  ferricyan- 
ide  is  added  to  a  cold  dilute  solution  of  a  ferrous  salt.  Potassium 
ferrocyanide  produces  a  bluish-white  precipitate  in  ferrous  iron 
solutions,  which,  however,  turns  rapidly  blue  as  it  absorbs  oxygen 
from  the  air. 

Ferric  Iron. — Potassium  ferrocyanide  when  added  to  a  solution 
of  a  ferric  salt  produces  a  deep  blue  precipitate  of  ferric-ferrocyan- 
ide,  Prussian  blue.  Potassium  ferrocyanide  deepens  the  color  of 
solutions  of  ferric  salts,  but  produces  no  precipitate. 

Ammonium  Sulphocyanate. — Ammonium  sulphocyanate  pro- 
duces a  blood-red  color  in  solutions  of  ferric  salts,  even  in  exceed- 
ingly dilute  solutions. 

Conversion  of  Ferrous  into  Ferric  Iron,  and  vice  versa. — By 
boiling  a  solution  of  a  ferrous  salt  with  a  few  drops  of  nitric  acid 
the  ferrous  iron  changes  to  the  ferric  state,  with  the  formation  of 
the  ferric  salt. 

Ferric  iron  may  be  reduced  to  ferrous  by  boiling  the  hydro- 
chloric acid  solution  with  metallic  tin  or  zinc  (2FeCls-fSn  = 
2FeCl2+SnCl2)  until  the  yellow  color  of  ferric  chloride  disappears. 

3.  Precipitation  with  Ammonium   Hydroxide. — When   ammo- 
nium hydroxide  is  added  in  excess  to  a  solution  of  a  ferric  salt,  a 
brownish-red   precipitate   of  ferric   hydroxide   is   thrown   down. 
This  is  the  most  convenient  way  of  removing  iron  from  a  solution. 
Ferrous  iron  should  be  converted  into  ferric  iron,   as  directed 
above,   before  attempting   to   precipitate   with   ammonia,    since 
ferrous  iron  is  only  partly  precipitated  and  forms  a  dirty-green 
precipitate.     Silica,  if  present,  should  be  removed,  see  §  1,  p.  57. 

4.  Detection  of  Ferrous  and  Ferric  Iron  in  Insoluble  Minerals.-— 
Fuse  thoroughly  a  small  amount  of  the  finely  powdered  mineral 
with  three  or  four  volumes  of  borax  in  a  large-sized  closed  tube, 
in  the  Bunsen  burner.     Crack  the  tube  about  the  fusion  while 
still  hot  by  touching  it  with  a  few  drops  of  cold  water.     Break 
the  end  off  and  boil  it  for  a  minute  in  a  test-tube  with  3  cc. 


44 


DETERMINATIVE  MINERALOGY 


of  previously  boiled  hydrochloric  acid,  dilute  with  a  little  previously 
boiled  water,  divide  quickly  into  two  parts,  and  tost  for  ferrous 
and  ferric  iron  as  directed  under  §  2  above. 

5.  Bead  Tests. — The  colors  imparted  by  the  oxides  of  iron  to 
the  fluxes  vary  considerably  with  the  amount  of  material  used, 
and  are  not  very  decisive.  They  are,  however,  frequently  met 
with  in  making  bead  tests,  and  it  is  well  to  bear  them  in  mind. 


Oxidizing 
Flame 

§ 
W 

BORAX 

SALT  OF  PHOSPHORUS 

LITTLE  OXIDE 

MUCH  OXIDE 

LITTLE  Oxrt>E 

MUCH  OXIDE 

Yellow 
Amber 

Brownish- 
Red 

Yellow 

Brownish-Red 

§ 
U 

Colorless 

Yellow 

Colorless 

Through  Yellow 
to  nearly  color- 
less 

Reducing 
Flame 

h 

o 
W 

Pale  Green 

Bottle 
Green 

Pale  Yellow 

Brownish-Red 

p 

1 

Colorless 

Pale  Green 

Through  Pale 
Green  to 
colorless 

Through  Yel- 
lowish-Green to 
colorless  or 
Pale  Violet 

Lead,  Pb— 207.2 

1.  Sublimate  from  Lead  Minerals  on  Charcoal. — Lead  minerals 
when  heated  B.B.  on  charcoal  yield  a  coating  of  lead  oxide,  or  if 
sulphur  is  present  and  the  mineral  is  heated  rapidly,  of  some 
combination  of  lead  oxide  and  sulphur  dioxide.  The  lead  oxide 
coat  is  rather  readily  volatile  in  both  flames.  It  is  orange-yellow 
when  hot,  fading  to  yellow  when  cold.  On  the  outside  the  coat- 
ing appears  bluish-white.  The  coating  obtained  from  lead  sul- 
phide when  the  latter  is  heated  rapidly,  is  yellow  only  quite  near 


SIMPLE  TESTS  FOR  THE  ELEMENTS  45 

the  assay,  and  is  a  dense  white  further  away,  bordered  with  blue. 
It  is  also  quite  volatile  and  resembles,  except  for  the  yellow  color 
near  the  assay,  the  coating  obtained  from  antimony,  with  which 
it  should  not  be  confused.  If  the  sulphur  is  first  carefully  roasted 
off,  the  normal  lead  oxide  coat  is  then  obtained  on  heating  in  the 
R.F.  Some  minerals  containing  lead,  antimony  and  sulphur, 
like  jamesonite,  give  a  very  volatile  coating,  on  charcoal  B.B., 
yellowish  or  brownish  yellow  near  the  assay,  white  to  bluish 
white  further  away.  Careful  roasting,  using  a  small  O.F.,  will 
give  an  antimony  oxide  sublimate  first  and  the  lead  oxide  coat 
may  be  obtained  later.  With  such  minerals  the  O.T.  test  should 
be  used  as  a  confirmatory  test.  To  detect  antimony  and  arsenic 
in  the  presence  of  lead  the  open-tube  test  may  be  used.  See  4, 
page  24,  and  3,  page  25. 

2.  Reduction  of  Lead  Minerals  to  Metallic  Lead  on  Charcoal. — 
For  this  test  mix  4  cmm.  of  the  mineral  to  be  tested  with  an  equal 
volume  of  charcoal  dust  and  three  or  four  volumes  of  sodium 
carbonate,  and  fuse  on  charcoal  B.B.  in  the  R.F.     Metallic  lead, 
if  present,  will  be  reduced  and  may  be  collected  into  a  globule. 
The  globule  is  bright  in  the  R.F.,  iridescent  in  the  O.F.,  owing  to 
a  film  of  oxides,  and  quickly  tarnishes  in  the  air  to  a  dull  gray. 
It  is  soft  and  highly  malleable.     B.B.  lead  is  somewhat  volatile, 
and  combines  with  oxygen  from  the  air,  depositing  on  the  char- 
coal as  a  coating  of  lead  oxide.     By  heating  in  the  O.F.  the  lead 
globule  may  be  entirely  converted  into  lead  oxide,  which  volatil- 
izes and  deposits  on  the  coal. 

The  above  test  is  very  characteristic,  but  is  sometimes  ren- 
dered doubtful  by  the  presence  of  other  elements,  especially 
bismuth.  For  the  method  of  separating  lead  and  bismuth  in  the 
wet  way,  see  3,  p.  30.  When  antimony  is  present  it  should  be 
removed  as  much  as  possible  by  roasting  in  a  very  small  O.F. 
before  reducing  with  sodium  carbonate  on  charcoal. 

3.  Iodine   Tests,   Distinction  between  Lead  and  Bismuth. — If 
a  coating  of  lead  oxide  be  moistened  with  a  few  drops  of  hydriodic 
acid  and  heated  in  a  small  blowpipe  flame,  a  chrome-yellow  deposit 
of  lead  iodide  is  formed.     When  very  thin  this  appears  greenish- 


46  DETERMINATIVE  MINERALOGY 

yellow.  This  deposit  is  readily  distinguished  from  bismuth 
iodide,  which  is  red.  The  same  coating  can  be  made  by  heating 
the  original  mineral  with  a  mixture  of  equal  parts  potassium 
iodide  and  sulphur,  in  an  oxidizing  flame,  on  charcoal  or  the 
plaster  tablet. 

4.  Precipitation  of  Lead  as  Chloride  or  Sulphate. — Lead  chloride 
or  lead  sulphate  may  be  thrown  down  in  the  form  of  white  pre- 
cipitates, from  not  too  concentrated  solutions  of  lead  minerals 
in  nitric  acid,  by  adding  hydrochloric  or  sulphuric  acid  respectively. 
The  chloride  is  quite  soluble  in  hot  dilute  acids  and  hot  water. 
It,  therefore,  will  frequently  not  precipitate  in  hot  solutions,  but 
comes  down  on  cooling  as  a  crystalline  precipitate.     Solutions 
of  lead   minerals   in   hot   dilute   hydrochloric   acid   will   deposit 
crystals  of  lead  chloride  on  cooling.     The  sulphate  precipitates 
as  a  finely  divided  white  powder  which  is  very  insoluble.     It 
may  be  filtered  off  and  tested  B.B.  on  charcoal. 

5.  Flame    Coloration. — Lead    minerals    when    heated    in    the 
R.F.,  either  in  the  forceps  (care  should  be  taken  not  to  alloy  the 
forceps)  or  otherwise,  impart  a  pale  azure-blue  color  tinged  with 
green  to  the  flame. 

Lithium,  Li — 6.9 

Lithium  minerals  can  usually  be  told  by  the  brilliant  crimson 
color  imparted  by  lithium  to  the  flame.  The  crimson  of  lithium 
is  sometimes  obscured  by  the  presence  of  other  substances, 
especially  sodium.  Where  only  a  little  sodium  is  present  it  may 
often  be  gotten  rid  of  by  first  heating  in  the  cooler  part  of  the 
flame  for  a  time  until  the  sodium  has  burned  off,  and  then,  where 
it  is  hotter,  when  the  lithium  flame  may  be  seen.  When  much 
of  the  interfering  substance  is  present  the  spectroscope  must  be 
resorted  to. 

No  lithium  minerals  give  an  alkaline  reaction  on  moistened 
test  paper  after  ignition,  which  will  serve  to  distinguish  them 
from  strontium  minerals. 


SIMPLE  TESTS  FOR  THE  ELEMENTS  47 

Magnesium,  Mg — 24.3 

1.  There  are  no  very  satisfactory  blowpipe  tests  for  magnesium. 
It  must  therefore  in  general  be  tested  for  by  the  regular  analytical 
methods.  These  involve  the  removal  from  the  solution  in  which 
the  magnesium  is  to  be  finally  precipitated  as  ammonium  mag- 
nesium phosphate,  of  all  interfering  elements,  according  to  the 
methods  prescribed  in  qualitative  analysis.  As  a  matter  of  fact 
in  the  ordinary  run  of  mineral  determinations,  magnesium  is  met 
with  in  minerals  where  the  interfering  elements  are  rarely  other 
than  silicon,  iron,  aluminium,  calcium,  and  very  small  amounts 
of  manganese,  and  these  can  be  removed  very  simply  and  quickly. 
Where  a  silicate  is  to  be  examined  the  method  of  procedure  is 
described  on  page  58,  §  4.  In  the  case  of  minerals  where  silica 
is  absent  it  is  only  necessary  to  carry  out  the  procedure,  beginning 
with  the  precipitation  of  iron,  etc.,  with  ammonium  hydroxide.  In 
any  case,  the  final  solution  containing  the  magnesium  should  be 
cold  and  strongly  alkaline  with  ammonia,  and  should  also  not  be 
too  dilute,  that  is.  it  should  not  exceed  15  cc.  in  volume  where 
the  original  amount  of  substance  was  from  0.1  to  0.2  of  a  gram. 
To  this  solution  an  excess  of  soluble  phosphate  (usually 
hydrogen  sodium  phosphate,  or  microcosmic  salt)  is  added.  If 
precipitation  does  not  result  at  once,  the  solution  is  allowed  to 
stand  for  some  time  with  occasional  stirring. 

2.  Magnesium  oxide,  hydroxide  or  carbonate,  if  ignited  B.B. 
after  moistening  with  cobalt  nitrate  solution,  assume  a  faint  pink 
color.  Slight  impurities  render  this  test  uncertain. 

Manganese,  Mn — 54.9 

Manganese  can  be  readily  detected  by  the  colors  which  it 
imparts  to  the  sodium  carbonate  or  borax  beads. 

1.  Sodium  Carbonate  Bead. — Minerals,  containing  even  a 
small  percentage  of  oxide  of  manganese,  if  finely  powdered  and 
fused  in  a  sodium  carbonate  bead  in  the  O.F.,  form  a  compound, 
sodium  manganate,  Na2MnC>4,  which  imparts  a  bluish-green 


48  DETERMINATIVE  MINERALOGY 

color  to  the  bead  when  it  is  cold.  This  is  a  very  delicate  test 
and  is  not  interfered  with  by  other  substances.  Larger  amounts 
of  powdered  mineral  fused  on  a  platinum  foil  with  sodium  car- 
bonate and  a  little  potassium  nitrate  (to  supply  oxygen)  over  the 
Bunsen  flame  may  be  used  to  detect  amounts  of  manganese  as 
small  as  a  fraction  of  1  per  cent. 

2.  Borax  Bead. — Small  quantities  of  manganese  oxide  dis- 
solve in  the  borax  bead  when  heated  in  the  O.F.,  coloring  it 
a  fine  reddish  violet.  If  the  bead  is  then  heated  in  a  strong, 
smoky  R.F.  for  some  time,  entirely  out  of  contact  with  the  air,  the 
color  may  be  wholly  destroyed  by  a  reduction  of  the  higher  oxide 
of  manganese  to  MnO,  which  forms  a  colorless  compound  with 
borax.  Too  large  amounts  of  manganese  will  give  a  black  or 
nearly  black  bead,  and  care  should  be  taken  to  avoid  such  an 
excess.  This  test  is  sometimes  rendered  unreliable  by  the  pres- 
ence of  other  oxides,  such  as  iron,  which  impart  a  color  to  the 
bead,  and  where  these  are  present,  or  suspected  to  be  present, 
the  sodium  carbonate  bead  should  be  used. 

Salt  of  Phosphorus  Bead. — The  colors  imparted  to  the  salt  of 
phosporus  bead  are  similar  to  those  obtained  with  borax,  but  are 
less  satisfactory. 

Mercury,  Hg— 200.6 

1.  Closed-tube  Test. — The  only  common  mercury  mineral  is 
the  sulphide,  HgS.  If  this  is  heated  alone  in  the  closed  tube  it 
sublimes,  and  deposits  on  the  cool  part  of  the  tube  as  a  black 
sublimate.  The  only  other  permanently  black  sublimate  obtained 
from  minerals  is  that  of  arsenic,  which  is  easily  distinguished  from 
the  HgS. 

Mercury  compounds  when  fused  with  sodium  carbonate  in 
the  closed  tube  are  decomposed  and  metallic  mercury  is  formed. 
This  distills  up  the  tube  and  collects  on  its  walls  as  a  gray  subli- 
mate composed  of  minute  globules  of  mercury.  These  globules 
may  be  collected  into  larger  ones  by  rubbing  them  with  a  wire 
or  match  end.  About  three  volumes  of  dry  sodium  carbonate 


SIMPLE  TESTS  FOR  THE  ELEMENTS  49 

should  be  mixed  with  the  mineral,  and  a  layer  of  the  same  dry 
carbonate  placed  on  top  of  the  mixture  in  the  tube,  so  as  to  catch 
and  react  with  any  of  the  mercury  mineral,  which  might  other- 
wise escape  by  volatilization.  We  may  illustrate  the  reactions 
which  take  place  in  the  closed  tube  with  the  mineral  cinnabar, 
HgS,  as  follows:  HgS+Na2C03  =  Hg+O+C02+Na2S. 

2.  Open-tube  Test. — The  sulphide  of  mercury  when  heated 
slowly  in  the  open  tube  yields  a  gray  sublimate  of  metallic  mercury. 
This  may  be  collected  into  globules  by  rubbing  with  a  match  end 
or  a  platinum  wire.  Mercuric  oxide,  which  is  formed  by  the 
reaction,  is  broken  down  by  the  heat  into  oxygen  and  mercury. 
The  latter  condenses  on  the  walls  of  the  tube. 

Molybdenum,  Mo — 96 

1.  Tests  for  Molybdenum  when  in  form  of  Sulphide.     Coating 
on  Charcoal. — If  the  sulphide  of  molybdenum  is  heated  for  some 
time  on  charcoal  in  a  strong  oxidizing  flame,  a  sublimate  of 
molybdenum  trioxide,  MoOs,  is  deposited  on  the  coal  a  short 
distance  from  the  assay.     The  sublimate,  which  is  easily  volatile, 
is  pale  yellow  when  hot,  nearly  white  when  cold,  and  is  often 
distinctly  crystalline.     If  the  sublimate  be  heated  for  an  instant 
in  the  reducing  flame,  it  assumes  a  fine  blue  color  due  to  a  partial 
reduction  of  the  MoOs.     Nearer  the  assay,  a  thin,  tarnished,  cop- 
per-colored coating  of  MoO2  can  be  seen. 

Molybdenite,  MoS2,  yields  a  yellowish  sublimate  of  MoOs  in 
the  open  tube  if  heated  for  some  time  at  a  high  temperature. 
The  sublimate  often  takes  the  form  of  a  mass  of  slender  crystals. 

2.  Test  for  Molybdenum  in  Molybdates.     Boil  a  small  quantity 
of  the  powdered  molybdate  with  about  3  cc.  of  hydrochloric  acid 
in  a  test-tube  until  the  acid  is  nearly  all  evaporated,  that  is, 
almost  to  dry  ness;   cool,  add  about  5  cc.  of  water  and  a  piece  of 
tin.     On  warming,  a  deep  blue  color  forms.     The  hydrochloric 
acid  decomposes  the  molybdate,  leaving  on  evaporation  molybdic 
acid,  which  is  reduced  by  the  tin  to  a  blue  compound. 

3.  Bead  Test  with  Salt  of  Phosphorus. — With  medium  quan- 


50 


DETERMINATIVE  MINERALOGY 


titles,  if  heated  in  the  O.F.,  the  bead  is  yellowish  green  when  hot, 
almost  colorless  when  cold.  In  the  R.F.  it  is  a  dirty  green  when 
hot,  turning  to  a  fine  green  on  cooling.  The  colors  obtained  with 
the  borax  bead  are  not  satisfactory. 

4.  Flame  Test. — Some  molybdenum  minerals  may  yield  on 
heating  a  pale  yellowish-green  flame  coloration.  This  is  inten- 
sified by  moistening  with  sulphuric  acid,  but  is  not  a  very  satis- 
factory test. 

Nickel,  Ni— 58.7 

1.  Bead  Tests. — Of  the  bead  tests  for  nickel,  those  with  borax 
are  the  most  reliable. 


Oxidizing 
Flame 

BORAX 

SALT  OF  PHOSPHORUS 

g 

s 

6 

Violet 

WITH  LIITLE 

WITH  MUCH 

Reddish 

Brownish  Red 

Reddish  Brown 

Pale  Yellow 

Reddish  Yellow 

Reducing 
Flame 

§ 

Q 

_3 

O 

O 

Becomes  opaque  from 
the  separation  of  metallic 
nickel. 

Remains    unchanged.       Heated 
with  a  grain  of  tin  the  bead  becomes 
colorless. 

2.  Colored  Solutions. — Nickel  colors  nitric  acid  solutions 
apple  green,  and  if  such  solutions  are  made  alkaline  with  ammonia, 
a  blue  color  is  obtained  which  resembles  the  blue  obtained  from 
copper  solutions  in  the  same  manner,  but  is  not  so  intense.  The 
flame  color,  or  other  tests,  will  serve  to  distinguish  copper  from 
nickel  minerals. 


SINGLE  TESTS  FOR  THE  ELEMENTS  51 

3.  Test  for  Nickel  in  Presence  of  Cobalt. — A  small  amount  of 
cobalt  will  obscure  the  bead  test  for  nickel  and  confuse  the  colora- 
tion in  acid  solution.  When,  therefore,  it  is  desired  to  test  for 
nickel  in  the  presence  of  cobalt,  the  following  method  may  be  used: 

The  powdered  mineral  is  dissolved  by  warming  in  a  few  cc.  of 
cone.  HNOs.  After  cooling  and  dilution,  any  residue  is  filtered 
off,  and  the  solution  is  made  alkaline  with  ammonia.  To  this 
solution,  when  hot,  a  solution  of  dimethylglyoxime  is  added. 
This  precipitates  the  nickel  in  the  form  of  a  bright  scarlet  precipi- 
tate. If  iron  is  present,  tartaric  acid  must  be  added  to  the  solu- 
tion before  the  ammonia,  in  order  to  prevent  the  precipitation  of 
the  iron  with  the  nickel. 

Niobium,  Nb  (Columbium,  Cb)— 93.1 

1.  Reduction  Test. — In  order  to  get  niobium  minerals,  which 
are  as  a  rule  very  insoluble  in  acids,  into  solution  for  this  test,  it 
is  best  to  decompose  them  by  fusion  on  a  large  loop  of  platinum 
wire  with  about  five  volumes  of  borax.  After  two  or  three  such 
fusions  have  been  made,  crush  the  resulting  beads  to  a  fine  powder 
and  boil  with  a  few  cc.  of  hydrochloric  acid.  If  this  solution, 
which  will  usually  be  clear,  is  now  boiled  with  a  piece  of  tin,  a 
persistant  blue  color,  due  to  the  reduction  of  the  niobium  by  the 
tin,  will  be  obtained.  If  considerable  titanium  is  present  it  will 
also  be  reduced,  but  will  show  a  violet  color  (see  titanium,  p.  69) 
before  the  blue,  due  to  niobium,  appears.  To  distinguish  tung- 
states,  which  also  give  a  blue  color  when  treated  as  above,  see 
under  tungsten,  p.  71. 

Nitrogen,  N— 14 

The  few  natural  nitrates  of  the  heavy  metals  are  readily  decom- 
posed with  the  evolution  of  nitrogen  dioxide  gas,  N02,  by  heating 
alone  in  the  closed  tube.  This  gas  is  easily  recognized  by  its 
odor  and  brown  color. 

NO2  is  given  off  by  nitrates  of  the  lighter  elements  when  they 
are  heated  in  the  closed  tube  with  potassium  bisulphate. 


52  DETERMINATIVE  MINERALOGY 


Oxygen,  O — 16 

1.  Oxygen  is  rarely  tested  for  directly  in  minerals,  but  its 
presence  or  absence  is  inferred  from  the  character  of  the  other 
component  elements  and  their  behavior.     A  few  higher  oxides, 
notably  those  of  manganese,  give  off  oxygen  when  heated  in  the 
closed  tube.     In  making  this  test  the  substance  is  placed  in  a  closed 
tube  in  which,  a  short  way  above  the  assay,  is  also  placed  a  splinter 
of  charcoal.     The  splinter  is  heated  to  redness  at  the  same  time, 
or  just  before,  the  substance  is  ignited.     The  oxygen,  which  will 
be  given  off  if  a  higher  oxide  is  present,  will  cause  the  splinter  to 
burn.     To  illustrate,  the  dioxide  of  manganese,  pyrolusite,  reacts 
as  follows:  3MnO2  =Mn3O4+2O. 

2.  When  some  of  the  higher  oxides  are  dissolved  in  hydro- 
chloric acid,  an  amount  of  chlorine  is  liberated  equivalent  to  the 
oxygen  which   is  in  excess  over  that  demanded  by  the  lower 
valence  of  the  metal.     The  higher  oxides  of  manganese,  which 
are  common  minerals,  are  often  tested  this  way.     To  illustrate 
again   with  one  of  them,   pyrolusite:    MnO2+4HCl  =  MnCl2+ 
2H2O+2C1.     The  chlorine  is  easily  recognized  by  its  pungent 
odor  and  its  bleaching  action  on  moist  litmus  paper. 


Palladium  (see  under  Platinum) 
Phosphorus,  P— 31 

1.  Flame  Test. — Most  phosphates  when  moistened  with  sul- 
phuric acid  and  ignited  B.B.  color  the  flame  a  pale  bluish-green. 
Many  yield  the  coloration  without  the  use  of  the  acid. 

2.  Ammonium    Molybdate     Test. — A    yellow    precipitate    of 
ammonium  phosphomolybdate  is  thrown  down,  when  a  nitric 
acid  solution  of  a  phosphate  is  added  to  an  ammonium  molybdate 
solution.     The  solutions  should  be  cold,  and  that  of  the  phos- 
phate added  a  few  drops  at  a  time  to  the  molybdate  solution. 
Phosphates  which  are  insoluble  in  nitric  acid  may  be  first  fused 
with  sodium  carbonate  and  then  dissolved.     If  it  is  found  neces-, 


SINGLE  TESTS  FOR  THE  ELEMENTS  53 

sary  to  use  some  other  acid  than  nitric,  the  acid  must  be  nearly 
neutralized  with  ammonia  before  the  precipitation  is  made. 
Molybdenum  forms  a  similar  compound  with  arsenic,  which 
comes  down,  however,  only  from  a  hot  solution,  hence  the  advisa- 
bility of  having  a  cold  solution  in  testing  for  a  phosphate. 

3.  Test  with  Metallic  Magnesium. — This  test  depends  upon 
the  formation  of  phosphine,  PHs,  which  is  recognized  by  its  dis- 
agreeable odor.  It  is  best  to  make  the  test  as  follows:  Roll 
closely  2  to  3  cm.  of  magnesium  ribbon  and  place  it  in  the  bottom 
of  a  closed  tube.  Surround  the  ribbon  with  the  finely  powdered 
mineral,  getting  as  close  a  contact  as  possible,  and  heat  intensely 
B.B.  (The  tube  should  be  pointed  so  that  if  an  explosion  occurs  the 
contents  will  not  be  shot  out  of  the  end  toward  any  one.)  Crack  the 
tube  with  water  while  still  hot,  moisten  the  contents  with  a  few 
drops  of  water,  and  note  the  odor. 

Platinum,  Pt— 195.2 

Platinum  is  recognized  by  its  silver-gray  color,  malleability, 
high  specific  gravity,  infusibility,  and  insolubility  in  any  single 
acid.  It  dissolves  in  aqua  regia,  and  if  its  solution  is  evaporated 
nearly  to  dryness,  taken  up  in  hydrochloric  acid,  again  evaporated, 
taken  up  in  a  little  water,  and  a  concentrated  solution  of  ammonium 
chloride  added,  a  yellow  precipitate  of  ammonium  platinic  chloride, 
(NH4)2PtCl6,  will  form. 

The  other  members  of  the  platinum  group,  Iridium,  Pal- 
ladium, Osmium,  etc.,  demand  highly  special  methods  for  their 
identification.  For  these  methods  see  paper  by  A.  A.  Noyes, 
"Technology  Quarterly,"  Vol.  XVI,  No.  2,  June,  1903,  or 
"  Qualitative  Analysis,"  Treadwell-Hall,  Vol.  I,  1916. 

Potassium,  K— 39.1 

1.  (a)  Flame  Test. — Volatile  potassium  compounds  color  the 
flame  a  pale  violet.  This  color  is  easily  obscured  by  other  sub- 
stances, especially  by  the  intense  yellow  flame  of  sodium.  It  is 
therefore  usually  necessary  to  use  a  rather  thick  blue  glass  to 


54  DETERMINATIVE  MINERALOGY 

absorb  the  interfering  color.  Through  this  the  potassium  flame 
appears  purplish  red  or  violet,  depending  on  the  shade  and  thick- 
ness of  the  glass. 

(6)  Silicates  and  other  minerals  containing  potassium,  which 
do  not  color  the  flame,  may  be  mixed  with  an  equal  volume  of 
powdered  gypsum,  CaSO4-2H2O,  and  introduced  into  the  Bunsen 
flame  on  a  fine  platinum  wire.  Potassium  sulphate  is  formed  by 
the  reaction  between  the  gypsum  and  the  mineral,  and  gives  the 
potassium  flame  color  if  viewed  through  the  blue  glass. 

2.  Precipitation    as     Potassium     Platinic    Chloride. — Hydro- 
chlorplatinic  acid  produces  in  concentrated  aqueous,  or  slightly 
acid  solutions  of  potassium  salts,  a  yellow,  crystalline  precipitate 
of  potassium  platinic  chloride,  K^PtCle.     The  addition  of  alcohol 
(95%)    renders    the    precipitation    complete.     Ammonium    salts 
must  be  absent,  as  they  form  a  similar  compound  (NH^PtClo, 
which  comes  down  as  a  yellow  precipitate.     Ammonium  salts 
may  be  removed  by  evaporating  the  chloride  solution  to  dryness 
and  igniting  the  residue  gently  until  all  fuming,  due  to  ammonium 
salts,  stops. 

Insoluble  silicates  must  be  fused  with  four  volumes  of  sodium 
carbonate,  the  fused  mass  dissolved  in  hydrochloric  acid,  evapo- 
rated to  dryness,  taken  up  in  a  few  cc.  of  water,  boiled,  an 
equal  volume  of  alcohol  added,  the  solution  filtered,  and  the  potas- 
sium tested  for  by  the  addition  of  a  few  drops  of  H^PtCle. 

3.  Precipitation  in   Potassium   Perchlorate. — The   dried   chlo- 
rides are  obtained  as  directed  under  §  2,  above.     These  are  just 
dissolved  in  two  or  three  drops  of  water,  filtered  if  necessary, 
brought   just   to   dryness  again,   and   1    or   2   cc.    of   perchloric 
acid  solution  is  added  together  with  10-15  cc.  of  80  per  cent 
alcohol.     A  white  crystalline  ppt.  indicates  potassium. 

4.  Alkaline   Reaction. — With   the   exception   of   the   silicates, 
phosphates,  and  the  salts  of  a  few  rarer  acids,  potassium  com- 
pounds give  an  alkaline  reaction  on  moistened  test  paper  after 
ignition  B.B. 


SIMPLE  TESTS  FOR  THE  ELEMENTS  55 


Rare  Earths 

The  so-called  rare  earth  elements  properly  include  two  groups, 
the  Cerium  earths,  cerium,  lanthanum,  and  didymium,  and  the 
Yttrium  earths,  yttrium,  erbium,  etc.  With  these  are  often 
included  thorium  and  zirconium.  They  often  occur  associated 
in  quite  a  number  of  rare  minerals,  which  also  frequently  con- 
tain other  elements,  such  as  uranium,  titanium,  niobium,  and 
tantalum.  They  are  detected  by  wet  methods,  which  are  in 
general  quite  complicated.  Below  are  given  directions  which 
will  enable  one  to  separate  and  detect  the  earths,  including  thorium 
and  zirconium.  For  more  complete  tests,  reference  must  be  made 
to  analytical  treatises  on  the  analysis  of  the  rare  earths. 

Wet  Tests  for  Rare  Earths. — If  insoluble  *  in  acids  the  sub- 
stance is  decomposed  by  fusion  with  sodium  carbonate,  or  if  this 
flux  does  not  readily  effect  decomposition,  borax  may  be  used  (cer- 
tain niobates,  etc.),  and  silica,  if  present,  is  removed,  as  directed  on 
page  58.  A  small  excess  of  ammonium  hydroxide  is  now  added 
to  the  hot  solution,  and  any  precipitate  formed  is  quickly  filtered 
and  washed  with  hot  water.  This  precipitate  will  contain  the 
earths,  and  may  also  contain  a  variety  of  other  elements  which 
are  thrown  down  with  ammonia,  but  the  alkali  earths  will  pass 
into  the  filtrate.  The  precipitate  is  next  dissolved  in  dilute  nitric 
acid,  and  the  solution  evaporated  to  dryness  (the  last  part  of  the 
evaporation  should  be  carried  out  on  a  water  bath  to  avoid  over- 
heating the  residue). 

The  residue  is  taken  up  in  a  little  warm  water,  and  to  the 
boiling  solution,  a  hot  solution  of  strong  oxalic  acid  is  added  in 
excess.  The  solution  is  allowed  to  stand  for  some  hours  in  a  warm 
place,  then  filtered  and  washed.  The  precipitate  contains  the 
earths  and  thorium  as  oxalates;  the  filtrate  contains  any  zirconium 
and  uranium.  These  may  be  tested  for  as  directed  on  pp.  75,  71. 

The  precipitated  oxalates  are  next  ignited  in  a  crucible  for 

*  Several  rare  earth  minerals,  which  are  not  attacked  by  HC1  or  HNO3, 
are  easily  decomposed  by  strong  H^SO-i.  After  cooling  and  dilution  with  water, 
the  solution,  filtered  if  necessary,  is  treated  with  ammonia,  etc.,  as  directed. 


56  DETERMINATIVE  MINERALOGY 

some  time  over  a  strong  Bunsen  flame  to  decompose  them  to 
oxides.  These  are  then  dissolved  in  as  little  nitric  acid  as  possible 
and  the  solution  evaporated  just  to  dryness.  To  the  dry  nitrates, 
a  cold  saturated  solution  of  potassium  sulphate  is  added,  also  a 
few  crystals  of  the  salt  to  insure  saturation.  Allow  to  stand  twelve 
hours  or  more.  The  cerium  earths  and  thorium,  if  present,  will 
form  insoluble,  double  sulphates.  These  may  be  filtered  off, 
washed  with  the  same  saturated  sulphate  solution,  and  dissolved 
in  water.  If  the  precipitate  is  large  it  is  advisable  to  repeat  the 
precipitation  as  double  sulphates  after  having  first  dissolved  the 
original  precipitate  in  water,  reprecipitated  the  earths  again  as 
hydroxides  with  potassium  hydroxide,  filtered,  washed,  redissolved 
in  nitric  acid,  and  evaporated  just  to  dryness  as  before.  In  any 
case,  the  cerium  earths  and  the  thorium  are  obtained  in  the  form 
of  dry  nitrates  as  just  described.  A  large  excess  of  hot  ammonium 
oxalate  solution  is  poured  over  them  and  the  whole  is  allowed  to 
stand  for  some  hours.  The  cerium  earths  are  precipitated  as 
oxalates,  while  the  thorium  is  held  in  solution.  The  thorium  may 
be  thrown  out  by  slightly  acidifying  the  filtrate  from  the  earths 
with  nitric  acid,  and  boiling.  The  thorium  may  be  further  tested 
by  igniting  the  precipitated  oxalate  (the  oxide  thus  obtained 
should  be  white),  dissolving  in  HNOs,  evaporating  to  dryness, 
and  taking  up  in  a  hot  ammonium  oxalate  solution,  when  it  should 
entirely  dissolve.  The  presence  of  cerium  is  indicated  if  the 
ignited  oxalates  yield  a  salmon-brown  oxide  on  ignition,  and  it 
may  be  further  tested  for  by  a  salt  of  phosphorus  bead  test.  In 
the  O.F.  the  bead  is  yellow  to  orange  while  hot,  fading  to  colorless 
when  cold.  If  the  nitrate  solution  has  a  distinct  pink  color, 
didymium  is  present. 

The  yttrium  earths,  if  present,  may  be  thrown  out  from  the 
sulphate  solution  by  adding  potassium  hydroxide.  The  precipi- 
tated hydroxides,  after  washing  and  ignition,  may  be  dissolved  in 
nitric  acid,  and  after  removing  the  acid  by  evaporation,  the  earths 
are  precipitated  as  oxalates  with  ammonium  oxalate. 

For  further  details  relating  to  the  detection  of  these  elements 
see  "  Qualitative  Analysis,"  by  Treadwell-Hall,  Vol.  I,  1916. 


SIMPLE  TESTS  FOR  THE  ELEMENTS  57 


Selenium,  Se — 79.2 

1.  Before  the  B.B.  on  Charcoal  and  in  the  Forceps. — The  rare 
element  selenium  and  its  compounds  when  heated  B.B.  in  the 
R.F.,  in  the  forceps  or  on  charcoal,  color  the  flame  an  intense  azure- 
blue,  and  give  off  a  peculiar,  disagreeable  odor  which  may  perhaps 
be   described   as   resembling   that   of   decomposed   horse-radish. 
On   charcoal,    if   much   selenium   is   present,    a   silvery    coating 
of  selenium  oxide,  SeC^,  is  obtained,  generally  bordered  on  the 
outside  by  a  reddish  or  brownish  coat  of  finely  divided  selenium. 
If  this  coat,  which  is  volatile,  is  touched  with  the  R.F.  an  azure- 
blue  flame  color  is  obtained. 

2.  Open  Tube  Reactions. — Se02  is  formed  as  a  sublimate  in 
the  open  tube.     It  fuses  to  colorless  globules,  sometimes  reddened 
by   the   presence   of   metallic   selenium.     These   crystallize   and 
whiten  on  cooling.     If  the  SeO2  is  volatilized  from  the  end  of  the 
tube  and  the  end  held  in  the  Bunsen  flame,  the  latter  will  be 
colored  azure-blue. 

3.  Closed  Tube  Reactions. — Selenium  is  set  free  from  some  of 
its  compounds  when  they  are  heated  in  the  C.T.  and  deposits  as 
fused  reddish  or  brownish  globules  on  the  walls.     Some  selenium 
oxide  is  generally  formed  and  deposits  with  the  selenium,  but  a 
little  further  up  the  tube. 


Silicon,  Si— 28.3 

Silicon  occurs  in  nature,  either  in  the  form  of  the  oxide,  Si02, 
or  in  combination  with  a  considerable  variety  of  bases  forming 
the  silicates,  salts  of  the  various  silicic  acids.  The  silicates  fall 
rather  sharply  into  three  groups  as  regards  their  behavior  toward 
the  common  acids,  HC1,  HNOs.  These  are: 

1.  Silicates  which  Yield  a  Jelly  upon  Evaporation  with  Adds. — 
If  the  fine  powder  of  a  silicate  of  this  group  be  boiled  with  dilute 
nitric  or  hydrochloric  acid  and  evaporated,  a  point  is  finally 
reached  where  the  solution  thickens,  owing  to  the  separation  of 
silicic  acid  as  a  gelatinous  mass.  On  evaporating  this  to  dryness, 


58  DETERMINATIVE  MINERALOGY 

the  silicic  acid  is  dehydrated  and  a  residue  of  insoluble  silica, 
Si02,  is  left.  The  silica,  after  warming  with  dilute  HC1,  may 
be  filtered  off  and  thus  completely  removed  from  the  solution, 
which  may  then  be  tested  with  (see  §  4)  appropriate  reagents  for 
the  other  elements  present.  The  silica  may  be  examined  as 
directed  under  §  5  or  §  6. 

2.  Silicates   which   are    Decomposed   by    Boiling   with    Dilute 
Acids,  with  the  Separation  of  Non-gelatinous,  Powdery  or  Flakey 
Silica. — Silicates  of  this  group  are  often  mistaken  for  insoluble 
minerals,  that  is  to  say,  the  silica  suspended  in  the  solution  is 
mistaken  for  undissolved  mineral.      In  order  to  be  sure  that  de- 
composition has  occurred,  it  is  best  to  filter  off  the  silica,  and 
either  evaporate  a  drop  or  two  of  the  filtrate  on  a  piece  of  glass  or 
platinum  to  see  if  a  residue  of  dissolved  bases  remains,  or  test  the 
filtrate  with  reagents  as  directed  under  §  4,  to  see  if  it  contains 
any  bases  in  solution. 

3.  Silicates   which   are   Insoluble  in   Acids. — Most   insoluble 
silicates  may  be  completely  decomposed  by  fusion  with  four  to 
five  parts  of  sodium  carbonate.     In  the  few  cases  where  this  is 
not  effective,  borax  may  be  used.     The  fusion  may  be  made  on 
charcoal  or  on  a  large  loop  of  platinum  wire,  or  in  a  platinum 
capsule.     From  0.1  to  0.2  of  a  gram  of  very  finely  powdered  mineral 
should  be  used  in  making  this  fusion.     After  the  fusion  is  made 
the  pulverized  mass  is  dissolved  in  dilute  nitric  acid  (5  cc.  of 
6N.  HNOs)  in  a  test-tube,  and  evaporated  to  dryness. 

Toward  the  end  of  the  evaporation  gelatinous  silica  will  usually 
separate  from  the  solution.  The  dry  residue  in  the  tube  should 
now  be  moistened  with  a  few  drops  of  hydrochloric  acid  and  boiled 
with  5  or  10  cc.  of  water.  This  treatment  leaves  the  silica  as  an 
insoluble  powder  in  the  solution,  while  the  bases  are  dissolved. 
The  silica  may  be  filtered  off  and  tested  according  to  §  5  or  §  6. 
The  filtrate  may,  if  desired,  be  examined  for  bases  as  described 
under  §  4. 

4.  Special   Method   of   Procedure  for   Detecting   the   Common 
Bases  in  Silicates. — As  the  great  majority  of  the  silicates  met 
with  in  practice,  contain  as  bases  one  or  more  of  the  common 


SINGLE  TESTS  FOR  THE  ELEMENTS  59 

elements  only,  viz.,  sodium,  potassium,  calcium,  magnesium,  iron, 
and  aluminium,  very  simple  analytical  methods  may  be  used  in 
determining  their  composition.  The  following  directions,  if 
followed  closely,  will  be  found  rapid  and  convenient.  With  care 
the  whole  operation  can  be  carried  out  in  test-tubes,  although  a 
small  casserole  is  convenient  for  the  evaporation. 

To  the  filtrate  from  the  silica  (§3,  above)  separation  contain- 
ing the  bases  in  solution,  add  ammonium  hydroxide  in  slight  ex- 
cess, when  the  iron  and  aluminium  will  be  precipitated,  if  present, 
as  hydroxides.  If  the  precipitate  is  light  colored,  iron  is  absent,- 
or  present  in  small  amount.  The  precipitate  is  now  filtered, 
washed  with  hot  water,  transferred  from  the  filter  to  a  test-tube, 
about  5  cc.  of  water  and  a  small  piece  of  potassium  hydroxide 
are  added,  and  the  solution  boiled.  The  aluminium  hydroxide  goes 
into  solution,  leaving  the  ferric  hydroxide  undissolved.  If  the 
latter  is  filtered  off,  the  aluminium  in  the  filtrate  may  be  precipi- 
tated with  ammonia,  after  being  distinctly  acidified  with  hydro- 
chloric acid.  This  precipitate  may  be  filtered  off  and  tested 
according  to  1,  p.  22. 

The  filtrate  from  the  iron  and  aluminium  precipitation  is  now 
heated  to  boiling  and  a  hot  solution  of  ammonium  oxalate  added 
slowly.  Calcium,  if  present,  will  be  precipitated,  and  after  boil- 
ing a  minute,  is  filtered.  The  calcium  oxalate  may  run  through 
the  filter  at  first,  but  by  passing  the  solution  through  once  or  twice 
more,  this  may  be  stopped.  The  precipitate  may  be  tested 
according  to  1  or  3,  pp.  32-33. 

The  filtrate  from  the  calcium  precipitation,  which  should 
smell  distinctly  of  ammonia,  is  cooled,  and  an  excess  of  sodium 
hydrogen  phosphate  is  added.  Magnesium  will  be  precipitated, 
if  present,  although  it  may  not  come  down  at  once,  so  that  it  is 
best  to  allow  the  test-tube  to  stand  a  while  after  adding  the 
phosphate  solution. 

For  the  detection  of  sodium  and  potassium,  see  p.  63  and  pp. 
53-54. 

5.  Test  in  the  Salt  of  Phosphorus  Bead. — Oxide  of  silicon 
dissolves  very  slowly  in  the  salt  of  phosphorus  bead,  so  that  if  a 


,60  DETERMINATIVE  MINERALOGY 

silicate  is  fused  in  such  a  bead  the  bases  go  into  solution,  leaving 
behind  a  residue  of  silica.  This  is  not,  however,  a  very  satis- 
factory test,  as  there  are  a  number  of  minerals  containing  no 
silica  which  dissolve  slowly  in  the  salt  of  phosphorus  bead. 

6.  Test  for  the  Oxide  of  Silicon. — Oxide  of  silicon,  if  mixed  with 
an  equal  volume  of  sodium  carbonate  and  fused  B.B.  yields  a  clear, 
but  not  usually  colorless,  glass  of  sodium  silicate.  A  clear  glass  is 
not  obtained  with  silicates,  with  one  or  two  exceptions.  A  small 
quantity,  2  to  4  cmm.,  is  about  the  right  amount  to  take.  The 
test  is  especially  adapted  for  testing  the  natural  oxides  of  silicon, 
quartz,  etc.,  and  also  for  testing  silica  separated  from  solutions 
of  silicates  as  described  above. 

Silver,  Ag— 107.9 

1.  Reduction  on  Charcoal. — Pure  silver  minerals  can  be  easily 
reduced  with  a  flux  on  charcoal  B.B.  to  metallic  silver,  which 
fuses  readily  and  can  be  collected  into  a  globule.  It  may  be  recog- 
nized by  its  bright,  silver-white  surface  and  its  malleability. 
The  globule  may  be  further  tested  by  dissolving  in  dilute  nitric 
acid  and  precipitating  the  silver  as  silver  chloride,  with  HC1  or  a 
soluble  chloride. 

About  three  volumes  of  flux  are  recommended  for  the  reduc- 
tion of  silver.  The  flux  may  be  either  sodium  carbonate  or  a 
mixture  of  sodium  carbonate  with  borax.  A  little  powdered 
charcoal  mixed  with  the  assay  facilitates  the  reduction.  Where 
volatile  metals  are  present,  such  as  sulphur,  arsenic,  or  antimony, 
the  mineral  must  be  carefully  roasted  in  the  O.F.  before  fluxing 
and  reducing.  Although  silver  itself  gives  no  coating  on  charcoal, 
when  it  is  associated  with  lead  and  antimony  the  coatings  obtained 
from  these  "elements  may  show  a  purplish  color,  which  is  said  to 
be  characteristic. 

When  small  amounts  of  other  reducible  metals  are  alloyed 
with  the  silver  globule,  they  may  often  be  removed  by  heating 
the  globule  on  a  clean  charcoal  surface,  in  a  borax  bead,  in  the 
O.F.,  whereby  the  impurities  are  oxidized  and  the  oxides  formed 


SIMPLE  TESTS  FOR  THE  ELEMENTS  61 

dissolved  in  the  borax.  With  larger  amounts  of  reducible  metals, 
assay  methods  must  be  resorted  to,  to  obtain  the  silver  in  a  pure 
form.  For  a  complete  and  elaborate  description  of  assay  methods 
adapted  for  the  blowpipe,  and  the  apparatus  used  in  carrying  them 
out,  the  student  is  referred  to  R.  H.  Richard's  "  Blowpipe  Silver 
Assay  Notes,"  and  Plattner's  "  Blowpipe  Analysis,"  translated 
by  Cornwall,  eighth  edition.  With  a  little  practice,  however, 
entirely  satisfactory  qualitative  and  approximate  quantitative 
results  may  be  obtained  in  the  manner  described  beyond.  Very 
small  quantities  of  silver  may  be  detected  in  this  way. 

2.  Cupellation  Method  of  Detecting  Silver  in  Minerals  and 
Ores. — Mix  about  0.2  gram  of  ore  with  an  equal  volume  each  of 
borax  glass  and  test  lead  (pure  lead),  and  transfer  to  a  deep, 
funnel-shaped  cavity  in  a  nearly  square  piece  of  compact  charcoal. 
Fuse  the  assay,  heating  gently  at  first  to  prevent  mechanical  loss, 
in  the  smoky  reducing  flame  until  the  lead  is  all  collected  into  a 
single  globule.  This  is  accomplished  by  manipulating  the  assay, 
always  completely  covered  with  the  R.F.,  so  that  the  lead  globule, 
or  button,  passes  through  every  portion  of  the  melted  assay. 
For  this  manipulation  the  charcoal  is  conveniently  supported 
on  the  point  of  a  jackknife  or  a  forked  piece  of  wire  stuck  into 
the  under  side  of  the  coal.  The  coal  can  thus  be  easily  turned 
to  present  all  sides  to  the  flame  at  will.  When  a  single  large 
globule  is  formed,  the  flame  is  changed  to  the  clear  O.F.,  which  is 
manipulated  much  as  the  R.F.  was  before,  and  the  globule  is 
made  to  move  through  the  melted  assay.  Lead  oxide  is  formed, 
and  passes  into  the  slag,  carrying  with  it  the  oxides  of  other 
metals,  except  silver,  which  were  reduced  in  the  lead  globule. 
The  lead  oxide  formed,  not  only  acts  as  a  flux  for  removing  impuri- 
ties, but  by  its  formation  reduces  the  size  of  the  lead  button. 
This  oxidation  should  be  continued  until  the  globule  is  perhaps 
2  to  3  mm.  in  diameter.  The  globule  should  now  have  lost  its 
spherical  shape,  and  on  cooling  should  have,  unless  impurities 
are  still  present,  a  lead-white  color,  tinted  slightly  yellow  by  a 
thin  coating  of  lead  oxide.  When  copper  is  present,  or  if  anti- 
mony or  arsenic  were  present  in  the  original  substance  and  have 


62  DETERMINATIVE  MINERALOGY 

not  been  entirely  volatilized,  the  button  appears  black.  Where 
this  is  the  case,  a  longer  heating  in  the  O.F.,  with  the  addition  of 
a  little  test  lead,  is  necessary  to  remove  the  impurities.  The 
button  is  now  removed  from  the  slag  and  freed  from  adhering 
particles  by  hammering  into  a  cubical  form.  A  cupel  of  bone-ash 
is  now  made  by  pressing  some  fine  bone-ash  firmly  into  a  large 
(say  1 J  cm.  in  diameter  and  5  mm.  deep)  shallow  cavity  on  another 
square  piece  of  charcoal,  with  the  rounded  end  of  an  agate  or  steel 
pestle.  The  surface  of  the  ash  should  be  smooth,  free  from  stray 
particles  of  ash  or  dirt,  and  must  be  thoroughly  dried  by  intense 
ignition  B.B.  The  button  is  now  placed  carefully  on  the  cupel, 
and  fused,  first  in  a  small  R.F.,  then,  far  out  in  the  O.F.  The 
lead  oxide  formed  is  absorbed  by  the  ash  and  takes  away  with  it 
the  last  traces  of  impurities.  The  globule  should  be  constantly 
moved  about  the  surface  of  the  cupel  and  the  oxidation  continued 
until  all  the  lead  is  removed.  This  point  may  be  told  by  the 
sudden  disappearance  ("  blick  ")  of  the  brilliant  play  of  colors 
on  the  surface  of  the  globule.  The  silver  bead  is  now  spherical 
and  should  be  of  a  perfectly  silvery-white  color.  The  bead  should 
not  adhere  tightly  to  the  cupel,  but  in  case  it  does,  it  is  a  sign  that 
it  is  not  yet  entirely  free  from  lead.  It  may  then  be  fused  in  the 
O.F.,  alone  on  a  clean  surface  of  the  charcoal,  or  with  borax, 
which  may  easily  be  dissolved  away  from  the  silver  in  hot  water 
and  hydrochloric  acid.  If  the  button  of  lead  is  so  large  that  the 
amount  of  oxide  formed  is  too  much  for  one  cupel  to  absorb,  two 
cupels  may  be  used  in  succession. 

For  quantitative  determinations,  weighed  quantities  of  ore 
are  taken,  0.2  to  0.3  gram  being  a  suitable  quantity.  The  final 
button  of  silver  is  then  weighed  accurately,  or  its  weight  is  esti- 
mated, after  measuring  with  a  scale  or  microscope,  the  diameter 
of  the  button,  which  is  approximately  spherical. 

Gold,  if  present  in  the  ore,  goes  with  the  silver.  It  may  be 
separated  by  boiling  the  globule  with  concentrated  nitric  acid, 
which  dissolves  out  the  silver.  The  gold  may  then  be  collected 
on  a  small  paper  filter.  The  filter,  carefully  folded  into  a  little 
lump,  is  gently  burned  on  a  smooth  surface  of  charcoal,  the  result- 


SIMPLE  TESTS  FOR  THE  ELEMENTS  63 

ing  ash  and  gold  powder  mixed  with  a  bit  of  borax-glass  and  fused 
B.B.,  so  as  to  bring  the  gold  into  a  globule.  The  borax  may  be 
dissolved  away  and  the  gold  weighed,  if  there  is  a  weighable 
amount.  Where  the  button  of  silver  and  gold  is  more  than  one- 
quarter  gold,  the  silver  cannot  be  all  dissolved  out  by  nitric  acid, 
hence,  in  cases  where  the  presence  of  considerable  gold  is  sus- 
pected, a  piece  of  pure  silver  (weighed  if  desired)  somewhat 
larger  than  the  button  should  be  fused  with  it,  after  which  the 
treatment  with  nitric  acid  may  be  carried  out. 

3.  Precipitation  as  Silver  Chloride. — Silver  is  precipitated 
when  hydrochloric  acid  or  a  soluble  chloride  is  added  to  a  nitric 
acid  solution  of  the  metal.  If  the  amount  of  precipitate  is  small, 
it  appears  as  a  white  turbidity  in  the  solution,  if  large,  it  is  thick 
and  curdy.  On  exposure  to  the  light  it  turns  purple.  Silver 
chloride  is  soluble  in  an  excess  of  ammonia. 

Metallic  globules,  obtained  from  fusions  on  charcoal,  are 
conveniently  tested  for  silver  by  dissolving  them  in  dilute  nitric 
acid  and  adding  a  few  drops  of  hydrochloric  acid. 

Sodium,  Na— 23 

1.  Flame  Test. — The  intense  yellow  flame  color  which  sodium 
compounds  impart  to  the  flame  is  an  exceedingly  delicate  test 
for  sodium  and  is  the  one  usually  used  for  its  identification. 
The  sodium  flame  is  entirely  absorbed  by  blue  glass,  and  in  the 
spectroscope  gives  a  single  broad  yellow  band.     The  flame  test 
is  so  delicate  that  it  may  be  obtained  from  fragments  of  minerals 
containing   no   sodium,   but   which  have   been  handled   and  so 
acquired  a  little  sodium  on  the  surface  from  the  fingers.     Unless, 
therefore,  a  persistent  coloration  is  obtained  it  should  not  be  taken 
as  evidence  of  the  presence  of  sodium. 

2.  Alkaline  Reaction. — Sodium  minerals,  with  the  exception 
of  the  silicates,  phosphates,  borates,  and  salts  of  some  rare  acids, 
if  ignited  B.B.,  give  an  alkaline  reaction  on  moistened  turmeric  or 
litmus  paper. 


64  DETERMINATIVE  MINERALOGY 


Strontium,  Sr— 87.6 

1.  Flame    Test. — Strontium    compounds    impart    a    brilliant 
crimson  color  to  the  flame.     The  flame  test  is  most  satisfactory 
when  made  by  introducing  a  little  of  the  fine  powder,  moistened 
with  HC1,  on  a  platinum  wire  into  the  edge  of  the  Bunsen  flame. 
Care  should  be  taken  not  to  confuse  the  red  of  strontium  with  the 
crimson  of  lithium,  or  the  yellowish-red  of  calcium,  when  hydro- 
chloric acid  is  used. 

2.  Alkaline   Reaction. — In   common  with  the   other   alkaline 
earth    metals   and   the   alkalies,    strontium    compounds    (except 
silicates  and  phosphates)  give  an  alkaline  reaction  on  moistened 
test  paper  after  intense  ignition  B.B.  (compare  reaction  of  lithium 
minerals  (p.  46)  which  give  no  alkaline  reaction). 

3.  Precipitation  as  Sulphate. — When  sulphuric  acid  is  added 
to  a  solution  containing  strontium  a  heavy  white  precipitate  of 
strontium  sulphate  is  formed.     This  precipitate,  although  some- 
what soluble  in  hot  water  and  hydrochloric  acid,  is  much  less  so 
than  the  calcium  sulphate,  and  this  fact  serves  to  distinguish  it 
from  the  latter.     If  the  solution  to  be  tested  is  concentrated  to  a 
small  volume  (2  or  3  cc.),  divided  into  two  parts,  and  one  of  them 
diluted  to  15  cc.  with  water,  it  will  be  found  that  sulphuric  acid 
produces  a  precipitate  in  both,  if  strontium  is  present,  although 
it  will  come  down  somewhat  slowly  in  the  dilute  solution.     (Com- 
pare Calcium,  p.  33.)     Some  of  the  precipitated  sulphate  may  be 
collected  on  a  filter  and  introduced  into  the  flame  on  a  platinum 
wire  to  test  it  for  the  crimson  flame  color. 

Sulphur,  S— 32 

The  method  to  be  used  in  testing  for  sulphur  depends  upon 
whether  it  is  in  the  form  of  a  sulphate  or  a  sulphide,  that  is,  com- 
.bined  with  oxygen  or  not. 

A.  TESTS  FOR  SULPHUR  IN  SULPHIDES 

1.  Heating  on  Charcoal;  Odor  of  Sulphur  Dioxide. — If  a  frag- 
ment of  a  sulphide  is  heated  in  the  forceps  or  on  charcoal  B.B.; 


SIMPLE  TESTS  FOR  THE  ELEMENTS  65 

the  sulphur  is  volatilized  and  burns  with  the  oxygen  of  the  air, 
forming  sulphur  dioxide,  SC>2,  which  is  recognized  by  its  extremely 
sharp,  pungent  odor.  This  test  is  even  more  effective  if  the 
powdered  mineral  is  spread  out  thinly  on  the  charcoal  and  roasted 
in  the  O.F.  In  the  case  of  a  few  sulphides  which  contain  a  rela- 
tively small  amount  of  sulphur,  such  as  Cu2S,  or  those  like  ZnS, 
which  oxidize  slowly,  also  sulphides  which  contain  arsenic,  the 
odor  of  SO2  may  not  be  easily  detected.  Hence  tests  §  2  or  §  4  are 
in  general  the  more  reliable.  Sulphur  itself,  and  a  few  sulphides, 
burn  with  a  pale  blue  flame. 

2.  Heating  in  the  Open  Tube. — If  a  little  of  a  powdered  sul- 
phide is  heated  in  the  open  tube,  as  directed  on  page  18,  sulphur 
dioxide  is  formed  and  may  be  detected  by  its  odor  at  the  upper 
end  of  the  tube.     A  piece  of  moistened  litmus  paper  will  turn  red 
if  held  in  the  escaping  fumes,  and  eventually  will  become  bleached 
if  much  SO2  is  present.     The  open  tube  test  for  sulphur  is  very 
delicate,  and  is  perhaps  the  most  satisfactory  "  sulphide  "  test, 
so  far  as  minerals  are  concerned.     The  formation  of  sublimates 
in  the  tube  does  not  interfere  with  the  test.     A  little  sulphur 
trioxide  is  often  formed  by  secondary  reactions  in  the  tube,  and 
appears  as  a  white  smoke. 

3.  Heating  in  the  Closed  Tube. — Some  sulphides  decompose 
when  heated  in  the  closed  tube,  and  give  off  a  part  of  their  sulphur, 
which  volatilizes  and  deposits  as  a  sublimate  on  the  walls  of  the 
tube.     It  is  dark  red  when  hot,  fading  out  gradually  to  a  light 
yellow  when  cold.     If  the  tube  is  broken  off  below  the  sublimate, 
and  heated  in  the  Bunsen  flame,  the  odor  of  S(>2  may  be  obtained. 

4.  Silver  Coin  Test. — A  very  satisfactory  test  for  sulphur  may 
be  made  by  heating  a  small  quantity  of  the  powdered  mineral  with 
about  three  volumes  of  sodium  carbonate  in  a  closed  glass  tube, 
until  the  mixture  is  fused,   after  which  the  tube  is  broken,  the 
fusion  placed  on  a  clean  silver  coin,  and  moistened  with  water. 
If  sulphur  is  present,  a  black  stain  will  be  formed  on  the  silver. 
The  sodium  carbonate  reacts  with  the  sulphide  forming  sodium 
sulphide  thus,  MS+NfteCOs^MCOa+NagS.     The  Na2S,  when 
placed   on  the   coin,   reacts  with   the  water  and   with    oxygen 


66  DETERMINATIVE  MINERALOGY 

from  the  air;  2Ag+Na2S+H2O+O  =  Ag2S+2NaOH.  The  fusion 
may  be  made  on  a  clean  piece  of  charcoal,  but  if  the  gas  flame  is 
used,  a  slight  reaction  is  often  obtained  from  sulphur  which  may 
be  present  in  the  gas. 

5.  Oxidation  with  Nitric  Acid. — When  a  sulphide  is  boiled  in 
concentrated  nitric  acid  it  undergoes  more  or  less  complete  solu- 
tion accompanied  by  oxidation.     A  portion  of  the  nitric  acid 
suffers  decomposition  in  such  a  manner  that  it  yields  water, 
oxides  of  nitrogen,  and  oxygen,  which  latter  oxidizes  part,  or  all, 
of  the  sulphur  to  sulphuric  anhydride,  SOs.     The  latter,  of  course, 
forms  sulphuric  acid  with  water,  and  may  be  tested  for  according 
to  B,  §  1.     Usually  more  or  less  sulphur  is  set  free  during  the  early 
part  of  the  reaction,  which  does  not  oxidize  readily  in  that  condi- 
tion and  so  remains  in  suspension.     This  is  especially  true  of 
those  sulphides  which  dissolve  readily  in  hydrochloric  acid  with 
the  evolution  of  hydrogen  sulphide  (see  §  6),  and  may  be  explained 
by  assuming  that  some  hydrogen  sulphide  is  set  free  and  at  once 
oxidized  by  the  action  of  the  nitric  acid,  forming  water  and 
sulphur  (H2S+O  =  H2O+S).     During  the  action  of  nitric  acid 
on  a  sulphide,  red  vapors  of  NO2,  nitrogen  dioxide  gas,  are  given 
off. 

6.  Solution   in    Hydrochloric   Acid;     Evolution   of    Hydrogen 
Sulphide. — Most  natural  sulphides  are  either  insoluble,  or  diffi- 
cultly soluble  in  hydrochloric  acid.     A  few,   however,   dissolve 
with   the   evolution   of  hydrogen   sulphide   gas,   which  may  be 
recognized    by    a    disagreeable    and    highly    characteristic    odor 
resembling  that  of  bad  eggs. 

B.   DETECTION  OF  SULPHUR  IN  SULPHATES 

1.  Precipitation  with  Barium  Chloride. — Barium  chloride, 
when  added  to  a  dilute  acid  solution  (hydrochloric  or  nitric) 
containing  a  sulphate,  produces  a  dense  white,  highly  insoluble 
precipitate  of  barium  sulphate,  BaSO.*.  If  the  mineral  is  insoluble, 
it  may  be  tested  according  to  §  2,  or  it  may  be  fused  with  five 
volumes  of  sodium  carbonate,  the  sodium  sulphate  thus  formed 


SIMPLE  TESTS  FOR  THE  ELEMENTS  67 

soaked  out  by  digesting  in  water,  freed  from  the  insoluble  car- 
bonate by  filtration,  acidified  with  hydrochloric  acid,  filtered 
again  if  necessary,  and  barium  chloride  added. 

2.  Reduction  to  a  Sulphide  and  Test  on  Silver  Coin. — Mix  a  little 
of  the  finely  powdered  mineral  with  four  volumes  of  sodium  car- 
bonate (best  dry)  and  one  of  charcoal  dust,  and  fuse  in  a  closed 
tube.  Sodium  sulphate  is  formed  during  the  fusion  and  is  reduced 
by  the  charcoal  present  to  sodium  sulphide,  thus:  MS04+ 
Na2CO3+2C  =  Na2S+MCO3+2CO2.  If  the  tube  is  now  broken 
and  the  contents  placed  on  a  silver  coin  with  water,  a  black  stain 
of  silver  sulphide  wih1  be  formed,  the  same  as  described  under 
A,  §4. 

2.  Decomposition  in  the  Closed  Tube. — Some  sulphates,  viz., 
those  with  weak  bases,  such  as  iron,  aluminium,  etc.,  break  down, 
giving  off  SOs  when  heated  intensely  in  the  closed  tube,  and  when 
water  of  crystallization  is  present,  as  is  usually  the  case,  they 
yield  acid  water  in  the  tube. 

Tantalum,  Ta— 181.5 

This  metal  usually  occurs  associated  with  niobium,  chiefly  in 
the  mineral  columbite,  and  in  a  few  others.  It  also  forms  nearly 
a  pure  tantalate  with  Iron  and  Manganese. 

To  detect  tantalum  in  the  presence  of  niobium  proceed  as 
follows : 

Fuse  thoroughly  the  finely  powdered  mineral  with  five  or  six 
volumes  of  potassium  bisulphate.  Digest  the  powdered  fusion 
with  an  excess  of  dilute  sulphuric,  finally  boiling.  Filter  off  the 
white  oxides  of  tantalum  and  niobium,  which  will  remain  behind 
if  these  elements  are  present,  and  dissolve  them  in  strong  hydro- 
fluoric acid  in  a  platinum  crucible  or  dish.  To  the  concentrated 
solution  thus  obtained,  a  concentrated  solution  of  potassium  fluo- 
ride is  added.  This  will  form  needle-like  crystals  of  K^TaFr 
and  flat  plates  of  K^NbFy  if  these  elements  are  present.  The 
former  is  much  less  soluble  in  water  (220  parts  water  dissolve 
1  part  of  salt)  than  the  latter.  On  boiling  the  water  solution  of 


68  DETERMINATIVE  MINERALOGY 

the  tantalum  salt  a  difficultly  soluble,  white  oxy chloride  of  tan- 
talum, precipitates  out.     This  is  a  very  delicate  test  for  tantalum. 

Tellurium,  Te— 127.5 

1.  Sulphuric  Acid  Test. — In  the  absence  of   manganese  com- 
pounds, a  delicate  test  for  tellurium  and  tellurides  may  be  made 
by  warming  a  little  finely  powdered  mineral  in  a  test-tube  with  a 
few  cc.  of  concentrated  sulphuric  acid,  when,  if  tellurium  is  present, 
the  solution  will  assume  a  characteristic  reddish- violet  color.     If 
the  solution  is  cooled  and  diluted,  the  color  disappears,  and  a 
grayish-black  precipitate  of  tellurium  is  thrown  down. 

2.  Fusion  in  Closed  Tube  with  Sodium  Carbonate  and  Carbon. — 
Tellurium  or  tellurides,  if  powdered,  and  mixed  with  about  three 
volumes  of  sodium  carbonate  and  some  charcoal  dust,  and  fused 
in  a  large  closed  tube,  will  yield  a  reddish-violet  colored  solution, 
if,  after  cooling,  water  is  introduced  into  the  tube.     If  this  solu- 
tion is  poured  out  and  exposed  to  the  action  of  the  air,  a  gray 
precipitate  of  tellurium  is  formed. 

3.  Test  with  KOH  and  Aluminium. — The  powdered  mineral 
is  gently  warmed   with  a  few  cc.  of  a  concentrated   solution  of 
KOH  and  some  finely  granulated  metallic  aluminium  in  a  test 
tube.     A  deep  purple  coloration  appears  in  the  solution  if  tel- 
lurium is  present.     This  is  a  very  delicate  test. 

4.  Heating  on  Charcoal. — Heated  B.B.  on  charcoal,  tellurium 
and  the  tellurides  form  a  white  sublimate  near  the  assay,  resem- 
bling somewhat  antimony  oxide.     A  brownish  coating  of  unoxi- 
dized  tellurium  is  usually  formed  on  the  coal  just  beyond  the 
white  sublimate.     The  sublimate  volatilizes  when  heated  B.B., 
and  gives  a  pale  bluish-green  fiame  color  when  the  R.F.  is  used. 

5.  Open-tube    Test. — A    white    smoke    of    tellurium    dioxide, 
TeO2,  forms  when  tellurium  or  tellurides  are  heated  in  the  open 
tube.     This  condenses  mostly  on  the  tube  near  the  heated  part. 
The  Te02  volatilizes  slowly  and  fuses  to  globules,  which  are  yellow 
when  hot  and  colorless  when  cold. 

6.  Closed    Tube. — Tellurium  volatilizes  when  heated   in  the 


SIMPLE  TESTS  FOR  THE  ELEMENTS  6^ 

closed  tube,  and  deposits  on  the  tube  in  the  form  of  black  globules 
having  a  metallic  luster.  A  little  TeO2  is  also  usually  formed 
by  combination  with  the  oxygen  in  the  tube. 

Thorium,  Th — 232.4  (see  Rare  Earths,  p.  55) 
Tin,  Sn— 118.7 

1.  Reduction  on  Charcoal. — Tin  may  be  easily  reduced  to  a 
metallic  state  from  its  minerals,  by  following  closely  the  following 
directions :   Mix  4  or  5  cmm.  of  finely  powdered  mineral  with  an 
equal  volume  of  charcoal  and  two  volumes  of  sodium  carbonate, 
moisten  with  water,  and  heat  B.B.  on  charcoal  in  a  strong  R.F. 
A  large  number  of  minute  globules  will  form,  if  tin  is  present, 
and  these  can  be  easily  collected  into  one.     The  globules  are 
bright  while  in  the  R.F.,  but  become  quickly  covered  with  a  coating 
of  oxide  when  exposed  to  the  air.     Some  tin  volatilizes  when 
strongly  heated,  and  deposits  as  a  coating  of  oxide,  SnC>2,  on  the 
coal  about  the  assay.     This  oxide  is  a  very  pale  yellow  when  hot 
but  white  when  cold.     It  is  not  volatile  in  the  O.F.  and  but  very 
slowly  in  the  R.F.     The  globules  are  very  easily  fusible  and  stay 
molten  for  some  time  on  the  coal.     They  are  malleable,  and  if 
placed  in  a  little  cavity  on  charcoal  and  heated  B.B.,  will  yield, 
not  only  a  coating  on  the  coal,  but  may  be  imbedded  in  a  thick, 
white  crust  of  SnO2,  which  does  not  volatilize  or  melt,  and  glows 
brightly.     The  oxide,  if  moistened  with  cobalt  nitrate  and  ignited, 
turns  green.     The  globules,  when  boiled  in  fairly  strong  nitric 
acid,  form  a  white  insoluble  compound,  metastannic  acid. 

2.  Oxidation  with   Nitric  Acid. — Sulphides  containing  tin  dis- 
solve in  nitric  acid    with    the    formation    of    a    white    powder, 
metastannic  acid. 

Titanium,  Ti— 48.1 

1.  Reduction  with  Tin. — This  test  is  not  applicable  to  sub- 
stances containing  less  than  3  per  cent  of  titanium;  for  these  §2 
must  be  used.  Fuse  thoroughly  4  or  5  cmm.  of  finely  powdered 


70  DETERMINATIVE  MINERALOGY 

mineral  with  five  or  six  volumes  of  sodium  carbonate  on  charcoal 
B.B.  Pulverize  the  fusion,  dissolve  in  hydrochloric  acid,  add  a 
piece  of  metallic  tin,  and  boil.  Filter,  if  necessary,  to  remove 
suspended  charcoal.  If  titanium  is  present  the  solution  will 
show  a  violet  color.  It  may  be  necessary  to  boil  the  solution 
down  to  a  small  volume  before  the  color  appears  if  the  amount 
of  titanium  is  small.  The  sodium  carbonate  forms  sodium 
titanate,  NaiTiQ*,  which  dissolves  in  the  hydrochloric  acid, 
forming  titanium  tetra-chloride,  TiCU.  This  is  reduced  by  the 
action  of  the  tin  to  the  tri-chloride,  TiCls,  to  which  the  violet 
color  is  due.  This  test  very  often  fails  because  the  mineral  was 
not  sufficiently  decomposed  during  the  fusion.  This  usually  is 
due  to  the  fact  that  the  powder  was  not  fine  enough,  or  that  the 
fusion  was  incomplete.  Minerals  which  cannot  be  decom- 
posed with  sodium  carbonate,  like  the  niobates  and  tantalates, 
may  be  fused  with  borax. 

2.  Test  with  Hydrogen  Peroxide. — This  test  is  an  exceedingly 
delicate  one  and  is  applicable  to  all  minerals  containing  titanium. 
Fuse  the  mineral  with  sodium  carbonate  as  directed  under  §  1. 
Dissolve  the  fusion  in  1  cc.  of  concentrated  sulphuric  acid  and 
1  cc.  of  water,  and  heat  until  the  solution  becomes  clear.     Cool, 
dilute  with  water  and  add  a  little  hydrogen  peroxide.     This  gives 
a  straw -yellow  to  deep  amber  color,  depending  on  the  amount  of 
titanium  present. 

3.  Salt    of    Phosphorus  Bead. — In  the  O.F.   the  bead,   well 
saturated  with  powdered  mineral,  is  yellow  when  hot,  colorless 
when  cold.     In  the  R.F.  it  is  yellow  when  hot,  and  on  cooling 
shows  a  delicate  violet  color.     The  test,  however,  is  not  very 
satisfactory,  as  it  is  apt  to  be  interfered  with  by  other  substances. 

Tungsten,  W— 184 

1.  Some  tungstates  are  decomposed  by  boiling  with  hydro- 
chloric acid,  with  the  separation  of  a  canary-yellow  oxide  of 
tungsten,  WOs.  If  a  piece  of  granulated  tin  is  boiled  in  such  a 
solution  a  blue  color  is  obtained,  due  to  a  partial  reduction 


SIMPLE  TESTS  FOR  THE  ELEMENTS  71 

(2WOs4-W02)  of  the  trioxide.     On  long-continued  boiling  the 
solution  becomes  brown,  owing  to  reduction  to  WO2. 

2.  Tungstates,  which  are  unaffected  by  adds,  may  be  decom- 
posed by  fusing  with  five  or  six  volumes  of  sodium  carbonate. 
The  fusion  is  pulverized  and  boiled  in  a  test-tube  with  5  to  10  cc. 
of  water.     Sodium  tungstate,  which  is  formed  by  the  fusion, 
goes  into  solution  and  is  separated  from  the  bases  by  filtering. 
The  filtrate,   acidified   with   hydrochloric   acid,   yields   a   white 
precipitate  of  tungstic  acid,  which  turns  yellow  on  boiling  if  a 
fair  amount  of  tungsten  is  present.     This  precipitate  boiled  with 
metallic  tin  yields  the  characteristic  blue  color.     This  is  a  very 
delicate  test. 

3.  The  Salt  of  Phosphorus  Bead  is  not  colored  by  tungstic 
oxide  in  the  O.F.,  but  in  the  R.F.  assumes  a  fine  blue  if  the  bead 
has  been  saturated  with  finely  powdered  material. 

Uranium,  U— 238.2 

Uranium  is  a  rare  element  which  occurs  in  only  a  few  minerals. 
The  colors  which  it  imparts  to  the  salt  of  phosphorus  bead 
generally  serve  to  identify  it.  When  other  substances  are  pres- 
ent, which  also  color  the  bead,  the  uranium  must  be  separated  by 
wet  methods,  and  then  may  be  tested  in  the  bead. 

1.  Salt  of  Phosphorus  Bead  Test. — With  a  medium  or  large 
amount  of  material  the  bead  in  the  O.F.  is  yellow  while  hot,  but 
becomes  yellowish-green  on  cooling.     Heated  in  the  R.F.   the 
bead  is  a  smoky  or  dirty  green  while  hot,  changing  to  a  fine  green 
when  cold.     The  colors  imparted  to  the  borax  bead  resemble 
those  imparted  by  iron,  and  are  not,  therefore,  very  reliable. 

2.  Separation  of    Uranium  in  the  Wet  Way. — First  dissolve 
the  mineral  in  hydrochloric  acid  (if  insoluble,  it  may  be  first 
decomposed  by  fusion  with   sodium  carbonate,  or  if  not  readily 
effected  by  this  flux,  borax  may  be  used),  and  almost  neutralize 
the  solution  with  ammonia,  after  which,  solid  ammonium  car- 
bonate is  added,  together  with  a  few  drops  of  ammonium  sulphide. 
The  solution  is  well  shaken  and  allowed  to  stand  a  few  minutes. 


72 


DETERMINATIVE  MINERALOGY 


By  this  process  the  uranium  is  retained  in  solution,  while  iron  and 
many  other  elements  with  which  it  is  apt  to  occur  are  precipitated. 
After  filtering,  the  nitrate  is  acidified,  boiled  to  expel  carbon 
dioxide,  and  ammonia  added  in  excess.  The  precipitated  uranium 
should  then  be  collected  on  a  filter  and  tested  in  the  salt  of  phos- 
phorus bead,  according  to  §  1. 


Vanadium,  V — 51 

1.  Bead  Reactions. — Vanadium  is  most  conveniently  detected 
by  the  color  it  imparts  to  the  fluxes,  particularly  the  salt  of  phos- 
phorus. 


Oxidizing 
Flame 

BORAX                               SALT  OP  PHOSPHORUS 

MEDIUM  TO  LARGE  AMOUNT  OF  MATERIAL 

§ 

B 

Yellow 

Yellow  to  Deep  Amber 

§ 

o 

Yellowish-green  to  Colorless 

Paler  than  above 

Reducing 
Flame 

s 

n 

| 

0 

Q 

Dirty  Green 

Dirty  Green 

Fine  Green 

Fine  Green 

The  amber  color  in  the  O.F.  with  salt  of  phosphorus  serves 
to  distinguish  vanadium  from  chromium. 

Where  other  substances  are  present  which  color  the  fluxes 
and  interfere  with  the  test,  the  mineral  to  be  tested  may  be 
fused  in  a  platinum  cup  with  four  volumes  of  sodium  carbonate 


SIMPLE  TESTS  FOR  THE  ELEMENTS  73 

and  two  of  potassium  nitrate,  the  fusion  digested  in  warm  water 
to  dissolve  the  alkali  vanadate  formed,  filtered,  and  the  filtrate 
slightly  acidified  with  acetic  acid.  Lead  acetate  added  to  this 
solution,  if  vanadium  is  present,  will  throw  out  a  light  yellow 
precipitate  of  lead  vanadate.  (Lead  chromate,  p.  37,  is  much 
more  yellow.)  The  precipitate  may  be  tested  in  the  salt  of 
phosphorus  bead. 

2.  Wet  test  for  Vanadium. — Vanadium  forms  vanadyl  salts 
of  the  type  of  diovanadyl-sulphate  V2O2(SO4)2  in  which  the  state 
of  oxidation  is  represented  by  ¥204.  If  a  solution  of  di vanadyl 
sulphate  is  treated  with  Na2CC>3  or  NHUOH,  avoiding  an  excess, 
a  grayish-white  precipitate  separates.  Vanadates  are  not  thus 
precipitated.  This  precipitate  dissolves  in  acids,  yielding  a  blue 
color,  but  in  alkalies  yields  a  brown  color. 

The  colorless  or  light  yellow  solutions  of  meta-,  pyro-  and 
ortho-vanadates  are  colored  intensely  orange  by  the  addition  of 
acids. 

If  H2S  is  conducted  into  a  strongly  ammoniacal  solution  of  a 
vanadate  or  hypovanadate,  the  solution  at  first  turns  yellowish 
red,  then  the  color  slowly  deepens  and  finally  becomes  a  character- 
istic, brilliant,  violet-red  color  when  the  solution  becomes  thor- 
ougly  saturated  with  H2S.  This  is  a  very  delicate  test. 

In  acid  solution,  H^S  produces  no  precipitate,  but  reduces 
vanadic  compounds  to  the  divanadyl  condition,  which  gives  a 
blue  color.  Alcohol,  oxalic  and  tartaric  acids  do  likewise. 

If  a  few  drops  of  hydrogen  peroxide  are  added  to  an  acid  solu- 
tion of  a  vanadic  salt,  and  the  solution  shaken,  it  becomes  a 
reddish-brown. 

Lead  acetate  precipitates  vanadic  acid  quantitatively  as  a 
yellowish  lead  vanadate,  PbsCVO/Os-  If  dilute  HNOs  is  present, 
the  similar  lead  chromate  is  not  precipitated  (see  §  1  above). 

Water 

Water  is  given  off  from  many  minerals  when  these  are  heated 
more  or  less  intensely.  Its  detection  is  often  important  in  the 
determination  of  a  mineral  species.  In  testing  for  water,  a  few 


74  DETERMINATIVE  MINERALOGY 

small  fragments,  or  a  little  coarse  powder  (never  fine),  are 
shaken  down  into  the  bottom  of  a  closed  tube  and  heated,  first 
gently  and  then  more  intensely,  finally  using  the  hottest  blow- 
pipe flame  attainable,  or  even  a  blast  lamp.  The  water  con- 
denses in  the  cool  part  of  the  tube.  If  only  a  slight  ring  of 
moisture  is  seen  it  does  not  indicate  that  water  is  an  essential 
constituent. 

Where  the  water  is  not  chemically  combined,  but  is  held  as 
"  water  of  crystallization  "  (illustrated  by  gypsum  CaSO4-2H2O) 
it  is  expelled  at  relatively  low  temperatures,  and  may  even  begin 
to  come  off  at  a  little  dbove  100°  C.  Minerals  such  as  Brucite, 
Mg(OH)2,  which  contain  hydroxyl,  usually  require  a  higher 
temperature  to  expel  the  water.  In  some  instances  a  bright  red 
heat,  maintained  for  some  time,  is  required  to  expel  all  the  water. 

Acid  Water. — The  hydrous  salts  of  certain  volatile  acids  with 
weakly  basic  elements,  such  as  iron,  aluminium,  copper,  and  zinc, 
are  decomposed  in  the  closed  tube,  and  yield  water  which  is 
acid  (detected  with  litmus  paper).  Certain  minerals  contain- 
ing fluorine  and  hydroxyl  also  give  off  acid  water  in  the  closed 
tube. 

Zinc,  Zn— 65.4 

1.  Heating  alone  on  Charcoal. — If  a  fragment  or  the  powder 
of  a  zinc  mineral  is  heated  intensely  in  the  reducing  flame  on 
charcoal,  a  small  coating  of  zinc  oxide  deposits  near  the  assay. 
As  a  rule,  the  first  indication  of  a  coating  seen  is  an  iridescent, 
purplish  film  deposited  just  beyond  the  spot  where  the  flame 
strikes  the  coal.  On  continued  heating  a  pale  yellow  coat  deposits 
which  fades  out  white  on  cooling.  It  is  not  volatile  in  the  O.F., 
but  is  slowly  volatile  in  the  R.F.  The  coating  moistened  with 
cobalt  nitrate  solution  and  reheated  B.B.  turns  green.  This 
coating  is  easily  obtained  with  the  sulphide  and  carbonate  of 
zinc,  but  is  more  difficult  to  secure  with  the  silicates.  In  order 
to  get  the  oxide,  the  metal  zinc  must  be  reduced  from  the  com- 
pound, hence  the  intense  heating  in  the  R.F.  required.  The  metal 


SIMPLE  TESTS  FOR  THE  ELEMENTS  75 

volatilizes  readily,  burns  in  the  air  to  the  oxide,  and  settles  on  the 
coal.  Globules  of  zinc  are  never  obtained  (difference  from  tin 
and  lead).  The  coating  is  generally  obtained  with  the  aid  of 
soda  more  satisfactory  than  without  it,  and  it  is  always  so  with 
the  silicates. 

2.  Reduction  with  Sodium  Carbonate  and  Charcoal. — Mix  a 
small  amount  of  finely  powdered  mineral  with  an  equal  volume 
of  sodium  carbonate  and  a  little  charcoal  dust,  moisten  to  a  paste 
with  water,  and  heat  strongly  in  the  R.F.     The  coat  of  ZnO 
obtained  is  the  same  as  described  above,  but  is  generally  heavier. 

3.  Reaction  with  Cobalt  Nitrate. — When  infusible  light-colored 
zinc  minerals,  except  silicates,  are  moistened  with  cobalt  nitrate 
and  heated  strongly  in  the  O.F.  they  assume  a  green  color.     This 
can  be  done  with  fragments  in  the  forceps,  but  it  is  much  better 
to  use  the  powdered  mineral  on  charcoal. 

Silicates  of  zinc  when  treated  in  this  way  assume  a  blue  color, 
usually  with  some  green.  It  is  due  to  the  formation  of  a  fusible 
cobalt  silicate  (?). 

Zirconium,  Zr— 90.6 

1.  Turmeric  Paper  Test. — This  is  the  only  short  test  for  zir- 
conium, and  yields  fairly  satisfactory  results  with  minerals  rich 
in   zirconium.     For  small   quantities   more   elaborate  analytical 
methods  must  be  employed.     Powder  the  mineral  finely  and  fuse 
thoroughly  with  five  to  six  volumes  of  sodium  carbonate,  dissolve 
the  fusion  in  hydrochloric  acid  and  introduce  into  the  solution  a 
piece  of  turmeric  paper,  which  will  turn  an  orange  color  if  zir- 
conium is  present.     It  is  best,  for  the  sake  of  comparison,  to  have 
a  piece  of  turmeric  paper  in  another  test-tube,  containing  hydro- 
chloric acid  of  about  the  same  strength  as  the  first. 

2.  Behavior  in  Solution. — Ammonium,  sodium,  and  potassium 
hydroxides  throw  down  zirconium  from  its  solutions  as  a  bulky 
white  precipitate  resembling  aluminium  and  beryllium  hydroxides, 
but  differing  from  these  in  not  dissolving  in  an  excess  of  potassium 
hydroxide.     If  such  a  precipitate  be  filtered  off,  washed,  dis- 


76  DETERMINATIVE  MINERALOGY 

solved  in  hydrochloric  acid,  and  evaporated  until  only  a  drop  or 
two  remains,  the  residue,  taken  up  in  water,  will  either  not  yield 
a  precipitate  when  oxalic  acid  is  added,  or  will  give  one  which 
goes  readily  into  solution  again  (difference  from  the  cerium 
metals,  page  55). 


CHAPTER  III 

TABULATED   LISTS    OF    REACTIONS,   ETC.,   USEFUL    IN 
DETERMINATIVE  MINERALOGY 

I.     Fusibility  Scale,  see  page  6 
n.    Metallic  Globules  and  Magnetic  Masses 

Gold. — Bright  when  hot  or  cold.  Color  yellow.  Quite  easily 
fusible.  Malleable.  Gives  no  coating  on  charcoal. 

Silver. — Bright  when  hot  or  cold.  Color  white.  Quite  easily 
fusible.  Malleable.  Gives  no  distinct  coating  on  charcoal. 

Copper. — Bright  when  hot.  Surface  black  when  cold.  Color 
red.  Not  easily  fusible.  Malleable.  Gives  no  coating  on  charcoal. 

Lead. — Bright  in  the  R.F.,  iridescent  in  O.F.  Dull  surface 
when  cold.  Color  lead-gray.  Easily  fusible.  Soft  and  malleable. 
Yellow  volatile  coating  of  PbO  on  charcoal. 

Bismuth. — Bright  in  R.F.  Surface  dull  when  cold.  Color 
gray.  Easily  fusible.  Rather  brittle  on  flattening  with  hammer. 
Yellow  volatile  coating  of  Bi2Os  on  charcoal. 

Tin. — Bright  in  R.F.,  dull  surface  on  cooling.  Color  white. 
Very  easily  fusible.  Soft  and  malleable.  White  nonvolatile 
coating  of  SnC>2  on  charcoal. 

Easily  fusible,  bright  metallic  globules  are  often  obtained  by 
heating  compounds  of  the  metals  with  the  volatile  elements, 
sulphur,  arsenic,  or  antimony.  They  are  usually  distinguished 
from  pure  metals  by  their  extreme  brittleness. 

Magnetic  globules  or  magnetic  masses  are  obtained  in  the 
R.F.  when  iron,  and  sometimes  when  nickel  and  cobalt  are  present. 

77 


78 


DETERMINATIVE  MNERALOGY 


III.     Closed  Tube  Reactions 

(a)   Residues  in  Closed  Tube 


Original  Color 

Color  after  Heating 

Substance 

green  or  blue. 

black. 

copper  minerals.. 

green  or  brown. 

black. 

iron  minerals. 

pink,  red,  brown. 

black. 

manganese     or     cobalt 

white  or  colorless. 

dark  yellow  to  orange 

minerals. 

or  brown  when  hot  ; 

lead  and  bismuth  min- 

yellow to  white  cold 

erals. 

white,  yellow  or  colorless. 

pale  yellow  hot,  white 

zinc  minerals. 

cold. 

(6)  Gases  in  Closed  Tube 


Color 
Colorless. 

Colorless. 
Colorless. 
Colorless. 

Reddish-brown  color. 
Reddish-brown  color. 
Violet-colored  vapor. 
Brown  smoke. 


Composition 
Carbon  dioxide. 

Sulphur  dioxide. 
Oxygen. 

Hydrofluoric  acid. 
Nitrogen  dioxide. 
Bromine. 
Iodine. 


Remarks 
White     ppt.     with     Ba(OH)2. 

Odorless. 

Sharp  irritating  odor. 
Odorless. 

Etches  the  glass.     Sharp  odor. 
Disagreeable  odor. 
Very  irritating  odor. 
Irritating  odor. 


Organic  material  Empyreumatic  odor. 


(c)  Sublimates  in  Closed  Tube 

Color.  Composition.  Remarks. 

Colorless.  Water,  H2O.  Liquid,  volatile. 

Pale  yellow  to  color- 
less. Tellurium  oxide,  TeO2.  Liquid  when  hot,  whitish  globules 

when  cold.     Slowly  volatile. 

Yellow  to  reddish.      Sulphur,  S.  Liquid  when  hot,  yellow  crystalline 

solid  when  cold.  Volatile.  May 
be  nearly  white  when  the 
amount  is  small. 


TABULATED  LISTS  OF  REACTIONS,  ETC. 


79 


Color. 
Red 

Deep  red  to  nearly 
black. 


Composition. 
Oxysulphide  of  Anti- 
mony. 

Sulphides  of  Arsenic. 


Remarks. 


Black  or  brown. 
Black  mirror. 

Black  mirror. 
Black  mirror. 

Black  globules. 
Gray  globules. 

Gray,  metallic 
mirror. 

White,  solid. 


Tarry  products. 
Oxysulphide  of  anti- 
mony, Sb2S2O. 
Arsenic,  As. 

Mercuric    Sulphide, 

HgS. 

Tellurium,  Te. 
Mercury. 

Arsenic. 


Chlorides  of  lead  and 
oxides  of  antimony, 
and  arsenic. 


Black  when  hot. 

Liquid  when  hot.  Reddish-yellow 
transparent  solid  when  cold. 
Volatile. 

Liquid. 

Slowly  volatile.  Black  when  hot, 
dark  red  when  cold. 

Gives  garlic  odor  if  heated  after 
breaking  tube. 

Volatile.  The  sublimate  rubbed 
very  fine,  becomes  red. 

Fusible  globules. 

Globules  may  be  united  by  rub- 
bing. 

Obtained  when  As  is  abundant. 
Garlic  odor  if  tube  is  broken  and 
heated. 

These  are  usually  rather  slight  sub- 
limates. 


IV.     Open  Tube  Reactions 


Odors  Obtained  in  Open  Tube.     Gases,  Vapors 


Odor  of  Burning  Sulphur. — Strong  pungent  odor  due  to  the 
formation  of  sulphur  dioxide  SO2.  Gas  bleaches  moistened 
litmus  paper  held  in  end  of  tube.  Very  delicate  test. 

Odor  of  Arsenic  (garlic  odor). — Obtained  when  arsenic  is 
driven  off  rapidly  and  incompletely  oxidized. 

Odor  of  Selenium. — A  peculiar,  nauseating  smell  (decaying 
horse-radish  odor)  obtained  from  volatilized  and  incompletely 
oxidized  selenium. 

Odor  of  Osmic  Oxide. — An  exceedingly  pungent  odor — poison- 
ous if  too  much  is  inhaled. 


80  DETERMINATIVE  MINERALOGY 


Table  of  Sublimates 

Color.  Composition,  etc.  Remarks. 

Black.  Oxysulphide  of  anti-  Black  when  hot,  red,  cold.   Slowly 

mony.  volatile. 

Black.  Arsenic  and  sulphide  Volatile.      Results  from  too  rapid 

of  mercury.  heating  (see  closed  tube  subli- 

mates of  arsenic,  antimony,  and 
sulphur  compounds). 

Red,  orange,  yellow,  Sulphides  of  arsenic.     The  arsenic  compounds  are  redder 
sometimes  mixed      Sulphur.  than  sulphur  and  do  not  fade 

with  white.  as  much.     Result  from  too  rapid 

heating. 
Red.  Oxysulphide  of  anti-  Black  when  hot.     Slowly  volatile. 

mony. 
Red.  Selenium.  Volatile.      With    selenious    oxide, 

see  below. 

Pale   yellow    when  Oxide  of  mloybdenum,  Generally  clouds  the  tube  for  some 
hot;  white  when       MoOs.  distance.    Often  crystalline. 

cold. 
White,  crystalline.    Arsenic  oxide,  As2O3.    Octahedral  under  the  microscope. 

Very  volatile. 

White.  Selenium  oxide,  SeO2.  Often    with    red,    finely    divided 

selenium.  Crystalline  prismatic. 
Volatile. 
White  to  pale  yel-  Tellurium    oxide,  Slowly  volatile. 

low.  TeO2. 

White.  Antimony    oxide,  Usually  as  a  ring  near  assay.     U. 

Sb2O3.  powdery,  some  times  cryst.    See 

next  below.     Slowly  volatile. 

Pale,    straw-yellow  Antimonate   of   anti-  Follows  along  the  tube  like  a  heavy 
when  hot,  white       mony.  smoke.     Infusible,  non-volatile, 

when  cold.  powdery.   Always  obtained  with 

Sb2O3  when  sulphur  is  present. 

White.  Sulphate  and  sulphite  Non-volatile,  infusible.     Obtained 

of  lead.  from  sulphide  of  lead  on  rapid 

heating. 

Gray.  Mercury,  Hg.  Volatile.    May  be  united  into  glob- 

ules by  rubbing. 


TABULATED  LISTS  OF  REACTIONS,  ETC.  81 


Residues  in  Open  Tube 

Orange  to  red  when  Oxide  of  lead.  Liquid  when  hot.    Obtained  from 

hot,     yellow     to  roasting  sulphides  or  carbonate, 

pale  yellow  when 
cold. 
Dark  red.  Oxide  of  iron,  Fe^Os.    Obtained   from  long  roasting   of 

sulphides,  etc. 

Black.  Oxides  of  iron,  man-  Obtained   from  long  roasting  of 

ganese,  copper  and       sulphides,  etc. 
cobalt. 

Yellow-green.  Oxide  of  nickel.  Obtained    fron  long    roasting   of 

sulphides,  etc. 


V.     Sublimates  on  Charcoal 

Color  Substances  Remarks 

White.  Arsenic  oxide,  As2O3.  Very  volatile.        Deposits  distant 

from   assay.        U.    accomp.   by 
garlic  odor. 
White ;     red   with-  Selenium    oxide,  Very  volatile.   Imparts  a  blue  color 

out,       steel-gray      SeO2.      The  red  is      to  R.F.     Peculiar  odor  of  selen- 

within.  Se.  ium  (like  decaying  horse-radish). 

White,    on   outside  Tellurium      oxide,  Dense,  volatile.       Heated  in  R.F., 

gray    slightly      TeO2.      The  gray      volt,     and     gives     bluish-green 

brown.  is  Te.  flame  color. 

White,    bluish    on  Antimony  oxide,  Dense,   volatile.        Deposits   quite 

outside.  Sb2O3.  near  the  assay. 

White.  Lead  chloride;  rarely  Volatile.    U.  deposits  distant  from 

chlorides  of  copper       assay.     Bluish  flame  color, 
and  mercury. 
Canary-yellow  Oxide  of  zinc,  ZnO.    Not  volatile  in  O.F.    Deposits  near 

when  hot,  white  assay.     Moistened    with    cobalt 

when  cold.  and  ignited,  turns  green. 

Faint  yellow  when  Oxide  of  tin,   SnO2.     Not  volatile  in  O.F.,  diff.  volatile 

hot,  white  when  in  R.F.     Moistened  with  cobalt 

cold.  nitrate  and  ignited  turns  green. 

Pale    yellow    when  Oxide    of    molybde-  Volatile    in    O.F.     Touched    with 

hot,  white  when       num,  MoO2.   Cop-       R.F.,  turns  to  a  fine  deep  blue. 

cold.      Bluish  on       per  red  coating  is       Obtained  from  heating  MoSa  in 

outside,  inside  a       MoO2.  strong  O.F. 

copper-red. 


82  DETERMINATIVE  MINERALOGY 

Color.  Substance.  Remarks. 

Pale  yellow  to  white,  Oxides  of  molybde-  Obtained  when  MoS2  is  heated  in 
may  be  mixed  num.  the  R.F. 

with  blue ;  copper 
red  nearer  assay. 

Yellowish  to  brown-  Sulphide  and  oxide  of  Very  volatile.  Obtained  when  sul- 
ish  coat  mixed  arsenic  mixed  some-  phides  of  arsenic,  with  or  with- 
with  and  bordered  times  with  arsenic.  without  other  metals,  are  heated 
with  white.  rapidly. 

Yellow    when    hot,  A  mixture  of  lead  ox-  Volatile  in  both  flames.    Resembles 
straw-yellow       ide,    lead    sulphite       antimony.    Obtained  from  heat- 
when  cold;  dense      and  sulphate  (?).  ing  sulphides  of  lead  rapidly, 
white,  with  bluish 
border       distant 
from  assay. 

Dark  yellow  when  Oxide  of  lead,  PbO.  Slowly  volatile  in  bloth  flames, 
hot,  sulphur-yel-  Moistened  with  hydriodic  acid 

low    when    cold,  and  heated  in  O.F.  a  yellowish- 

white    or    bluish  green  lead  iodide  is  formed, 

white  on  outside. 

Dark  orange-yellow  Bismuth  oxide,  Bi2O3.  Slowly  volatile  in  both  flames, 
when  hot,  yellow  Moistened  with  hydriodic  acid, 

to  orange-yellow  ,  and  heated  gives  a  reddish  to 

when  cold.  chocolate-brown  coat  of  bismuth 

iodide. 

Reddish  to  deep  Silver  when  accom-  May  be  obtained  when  small 
lilac.  panied  by  lead  and  amounts  of  silver  minerals  are 

antimony.  present  with  sulphides  of  anti- 

mony, lead,  and  zinc. 

Reddish-brown ;        Cadmium  oxide.  U.  very  slight, 

yellowish  distant 
from  assay. 

Purplish,  irides-  Small  amounts  of  cad-  U.  very  slight  and  often  obtained 
cent  coat.  mium  or  zinc  oxide.  from  zinc  minerals  before  the 

ZnO  deposits;  often  borders  the 
latter. 

VI.    Table  of  Sublimates  as  Obtained  on  Plaster  Tablets 

(see  p.  12) 

Only  sublimates   are  listed  here  that  are  equally  or  more 
characteristic  than  those  similarly  obtained  on  charcoal. 


TABULATED  LISTS  OF  REACTIONS,  ETC.  83 

Element.  Character  of  sublimate. 

Selenium.  Brick-red  to  crimson. 

Tellurium.  Deep  brown  coat. 

Cadmium.  Dark  brown  coat  shading  to  greenish-yellow 

and  again  to  dark  brown. 
Molybdenum.  Similar  to  that  on  charcoal,  perhaps  more 

striking. 

VII.  Table  of  Sublimates  Obtained  on  Plaster  and  on  Charcoal 

With  the  Aid  of  Hydriodic  Acid  or  Bismuth  Flux 

(see  p.  12) 

Element  Character  of  sublimate 

Lead.  On  Charcoal — Greenish-yellow. 

Plaster — Chrome-yellow. 

Bismuth.  Charcoal — Bright   red   band   with   fringe   of 

yellow. 

Plaster — Chocolate-brown    with    underlying 
scarlet.     With  ammonia  becomes  orange- 
yellow  and  later  cherry-red. 
Mercury.  Charcoal — Faint  yellow. 

Plaster — -Scarlet  with  yellow  if  slowly  heated. 
Antimony.  Charcoal— Faint  yellow. 

Plaster — Orange  mixed  with  peach-red. 
Tin.  Plaster — Brownish-orange. 

Selenium.  Plaster — Reddish-brown,  nearly  scarlet. 

Tellurium.  Plaster — Purplish-brown  with  dark  border. 

Molybdenum.  Plaster — Ultramarine-blue. 

VIII.    Bead  Reactions 

In  the  following  tables  many  bead  reactions  usually  given 
have  been  omitted  in  the  belief  that  they  are  as  a  rule  indecisive 
and  often  misleading.  Only  reactions  are  listed  here  that  are 
characteristic,  provided  the  test  has  been  performed  as  directed 
on  page  16.  Below,  under  the  heading,  Substance,  the  word 
accompanying  the  name  refers  to  the  relative  amount  of  powdered 
oxide  that  is  required  to  produce  the  colors  given  in  the  same 
horizontal  column.  By  "  small  "  is  meant  a  very  minute  amount 
— a  few  specks;  by  "  medium  "  is  meant,  say  0.5  cmm.,  by 
"  large  "  1  cmm.  up.  This  is,  of  course,  only  a  very  rough  way 
of  indicating  the  amounts  to  be  used,  but  it  will  perhaps,  serve  its 


84 


DETERMINATIVE  MINERALOGY 


purpose.  It  must  be  borne  in  mind  that  the  colors  listed  below 
are  those  yielded  by  pure  oxides.  Variations  of  color,  impossible 
to  describe,  may  be  obtained  from  mixtures  of  various  elements, 
each  one  of  which  gives  a  color  reaction. 

BORAX  BEADS 


OXIDIZING  FLAME 


REDUCING  FLAME 


Hot 

Cold 

Substance 

Hot 

Cold 

pale  yellow 

nearly  colorless 

Titanium,    me- 

grayish 

pale  violet 

dium 

yellow 

nearly  colorless 

Iron   or   Uran- 

pale green 

nearly  color- 

ium, medium 

less 

yellow 

yellowish-green 

Chromium, 

green 

green 

small 

yellow 

very  pale  yel- 

Vanadium, me- 

smoky green 

green 

lowish-green 

dium 

yellow 

pale  yellow 

Cerium,  me- 

dium 

deep  yellow  to 

yellow 

Uranium,   me- 

pale green 

pale  green  to 

orange-red 

dium  to  large 

nearly    ccl- 

orless 

deep  yellow  to 

yellow 

Iron,  large 

bottle-green 

fades  some 

orange-red 

on  cooling 

deep  yellow  to 

yellowish-green 

Chromium,  me- 

green 

fine  green 

orange-red 

dium  to  large 

pale  green 

blue-green 

Copper,  me- 

colorless   to 

opaque  red 

dium  to  large 

green 

with    large 

amount 

pale  green 

pale  blue-green 

Copper,    small 

nearly  color- 

less 

green 

yellow,    green, 

Mixtures  of  Fe, 

same  or 

blue 

Cu,NiandCo 

opaque 

blue 

blue 

Cobalt,  small 

blue 

blue 

violet 

reddish-brown 

Nickel,  me- 

opaque gray 

opaque  gray 

dium 

violet 

reddish-violet 

Manganese, 

colorless 

colorless 

small 

TABULATED  LISTS  OF  REACTIONS,  ETC. 


85 


SALT  OF  PHOSPHORUS  BEADS 


OXIDIZING  FLAME 


REDUCING  FLAME 


Hot 

Cold 

Substance 

Hot 

Cold 

yellow 

colorless 

Titanium,    me- 

yellow 

violet 

dium  to  large 

pale  yellow 

colorless 

Tungsten,  large 

dirty  blue 

fine  bluish 

yellow 

pale  yellow 

Vanadium, 

pale  smoky 

green 

small 

green 

yellow   to    deep 

colorless 

Cerium,     me- 

colorless 

colorless 

yellow 

dium 

yellow 

pale  yellowish- 

Uranium,   me- 

pale smoky 

fine  green 

green 

dium 

green 

yellowish-green 

colorless 

Molybdenum, 

smoky  green 

fine  green 

medium 

deep   yellow   to 

yellow  to  color- 

Iron, medium 

red,    yellow 

almost  color- 

brownish-red 

less 

to  large 

to     yellow 

less 

green 

deep   yellow   to 

yellow 

Vanadium,  me- 

smoky green 

fine  green 

deep  amber 

dium  to  large 

reddish   to 

yellow   to   red- 

Nickel, me- 

reddish to 

yellow  to  red- 

brownish-red 

dish  yellow 

dium 

brownish-red 

dish-yellow 

green 

pale  blue 

Copper,     small 

pale    yellow- 

pale  blue  to 

'  green 

nearly    col- 

orless, rare- 

ly red 

dark  green 

blue  or  blue 

Copper,  me- 

brownish- 

opaque  red 

green 

dium  to  large 

green 

greem 

yellow,  green, 

Mixtures  of  Fi, 

blue 

Cu,  Ni  and  Co 

smoky  green 

fine  green 

Chromium, 

smoky  green 

fine  green 

medium 

blue 

blue 

Cobalt,   me- 

blue 

blue 

dium 

grayish-violet 

violet 

Manganese, 

colorless 

colorless 

small 

. 

86 


DETERMINATIVE  MINERALOGY 


SODIUM  CARBONATE  BEADS 

In  the  O.F.  chromium  colors  the  sodium  carbonate  bead  a 
pale  yellow  when  cold. 

Manganese  even  in  small  amounts  imparts  a  bluish-green 
color  to  the  cold  bead. 

In  the  R.F.  soda  beads,  if  colored  at  all,  are  generally  black, 
brown,  or  gray,  and  are  not  distinctive. 


IX.     Colors  Obtained  by  Heating  B.B.  with  Cobalt 
Nitrate  Solution 


Fragments  may  be  used,  but  the  fine  powder  made  up  into  a 
small  pile  on  charcoal,  moistened  with  the  cobalt  nitrate  and  then 
intensely  ignited  B.B.  gives  a  more  reliable  result. 


Color. 


Blue. 


Blue. 

Green  or  bluish 

green. 
Green. 


Dirty  Green. 
Pale  pink  or  flesh 

color. 
Lavender. 


Substance. 

Infusible  Aluminium 
minerals  which  are 
light  colored  or 
white,  or  become 
white  on  heating 
B.B. 

Infusible  silicate  of  zinc. 

Oxide  of  tin. 

Oxide  of  zinc;  zinc 
minerals  except  the 
silicates. 

Oxide  of  antimony 

Magnesian  oxide 

Berryllium  oxide 


Remarks. 

The  powder  or  a  fragment  re- 
quires very  intense  ignition  as 
a  rule. 


Applies  to  coating  on  charcoal. 

Strong  O.F.  is  usually  required, 
and  color  does  not  show  well 
until  cold. 

These  colors,  if  obtained  at  all, 
are  U.  indecisive. 


TABULATED  LISTS  OF  REACTIONS,  ETC. 


87 


X.     Flame  Colorations 


Color 

Crimson 
Crimson 

fellow-red 

Yellow 

Yellowish-green 

Yellowish-green 

Bright  green,  slightly  yellowish 

Pale  green 

Emerald-green 

Pure  green 

Pale  bluish-green 

Bluish-green  (flashes) 

Bluish-green 

Pale  blue 

Azure-blue 

Pale  azure-blue,  tinged  with  green 

Azure-blue 

Pale  violet 


Element. 


Lithium 
Strontium 


May  be  rendered  yel- 
lowish by  contami- 
nation with  sodium. 

Calcium 

Sodium 

Barium 

Molybdenum 

Boron 
f  Tellurium 
j  Antimony 
I  Lead 

Copper  oxide,  and  iodide 

Thallium 

Phosphorus 

Zinc 

Tellurium 

Arsenic 

Selenium 

Lead 

Chloride  of  copper 

Potassium  Use  a  blue  glass  to  cut 

out  sodium 


XI.     Colored  Solutions  Obtained   from  Minerals  with  Acids 


Color.  Acid, 

yellow  to  deep  yellow  HC1 

or  orange 
Yellow  to  brownish          HC1 


Elements  and  Remarks. 
Ferric  iron 


Higher  oxides  of  manganese.     Odor  of 

chlorine 
Pink  to  pale-rose  HNO3  Cobalt.    Turns  brown  then  reddish  on 

addition  of  excess  of  NH4OH. 
Pale  green  HNOs  Nickel  turns  blue  on  addition  of  excess 

of  NH4OH 
Green  or  bluish-green      HNO3  HC1     Copper,  turns  deep  blue  upon  addition 

of  excess  of  NH4OH. 
Blue-green  H2SO4  Same  as  next  above 


88  DETERMINATIVE  MINERALOGY 

XII.    Residues  Obtained  in  Acid  Solutions  of  Minerals 

White  Powdery. — Silica. — Obtained  from  many  silicates  when 
bdiled  with  acids.  These  are  all  non-metallic  in  luster. 

White  Powdery.— PbS04,  SbO2(OH),  Sn02.  Obtained  from 
a  number  of  metallic  sulphides  containing  either  lead,  antimony, 
or  tin,  when  treated  with  cone.  HNOs. 

Yellow,  Powdery. — Obtained  from  tungsten  minerals  with 
HC1.  Turns  blue  when  boiled  with  tin. 

Yellow,  spongy  masses,  or  melted  globules  of  sulphur  are 
obtained  when  certain  sulphides  are  boiled  in  nitric  acid. 

Gelatinous  Mass. — Silicic  acid. — Colorless  to  yellow.  Obtained 
on  evaporation  of  the  acid  solutions  of  many  silicates. 


CHAPTER  IV 

THE  DETERMINATION  OF  MINERALS, 
USE  OF  TABLES,  ETC. 

General  Remarks. — No  special  method  of  procedure  can  be 
laid  down  for  the  determination  of  minerals.  The  experienced 
mineralogist  can  usually  recognize  at  sight  the  more  common  or 
important  species,  or  at  least  will  need  to  make  only  one  or  two 
simple  tests  to  render  certain  their  identification.  In  the  case 
of  the  less  common  species,  or  of  common  ones  of  unusual  appear- 
ance and  habit,  he  may  have  resort  to  a  more  careful  examination 
involving  a  determinatioh  of  the  physical  and  chemical  properties, 
and  in  so  doing  may  have  to  employ  microscopic  methods  and  use 
polished  surfaces  or  thin  slices.  In  all  such  work  it  is  usually 
necessary  to  refer  to  standard  textbooks  of  mineralogy  1  in  which 
are  collected,  in  a  systematic  manner,  the  data  regarding  the  vari- 
ous mineral  species  and  their  varieties.  He  is,  furthermore,  often 
greatly  aided  in  such  an  examination  by  the  use  of  "  determinative 

xThe  following  is  a  list  of  books  in  English  on  Descriptive  Mineralogy: 

A  System  of  Mineralogy  (encyclopedic),  by  James  D.  and  E.  S.  Dana.  John 
Wiley  &  Sons,  Inc.  Also  Appendices  Nos.  1,  2  and  3. 

Dana's  Textbook  of  Mineralogy,  Third  Edition,  by  W.  E.  Ford.  John 
Wiley  &  Sons,  Inc. 

Study  of  Minerals  and  Rocks,  by  A.  F.  Rogers.     McGraw-Hill  Book  Co. 

Mineralogy,  Etc.,  by  A.  J.  Moses  and  C.  L.  Parsons.     D.  Van  Nostrand  Co. 

Mineralogy,  by  E.  H.  Kraus  and  W.  F.  Hunt.     McGraw-Hill  Book  Co.,  Inc. 

Mineralogy,  by  A.  H.  Phillips.     Macmillan  Co. 

Mineralogy,  by  W.  S.  Bayley.     D.  Van  Nostrand  Co. 

Mineralogy,  by  H.  A.  Meirs.     Macmillan  Co. 


90  DETERMINATIVE  MINERALOGY 

tables  1  "  in  which  the  various  minerals  are  arranged  according 
to  some  carefully  arranged  scheme. 

The  beginner,  or  worker  of  small  experience,  will  in  general 
save  much  time  and  effort,  and  arrive  at  a  satisfactory  result  with 
greater  certainty,  if  he  uses  one  of  these  "  determinative  "  tables, 
supplemented  always  by  reference  to  a  reliable,  descriptive  text. 

Of  those  tables  which  do  not  involve  the  use  of  the  microscope 
with  polished  surfaces  or  thin  slices,  it  may  be  said  that  they  fall 
under  three  types. 

In  the  first,  the  distinction  between  the  different  minerals  is 
based  entirely,  or  very  largely,  on  the  physical  properties,  such 
as  color,  hardness,  streak  and  crystalline  characters,  etc.  If 
chemical  and  blowpipe  characters  are  used,  they  are  given  a  very 
subordinate  place.  Such  tables  are  often  useful  where  pure  and 
easily  isolated  minerals  are  in  question,  particularly  where  the 
mineral  is  seen  to  possess  some  striking  and  easily  distinguished 
character,  such  as  a  simple  crystal  form  or  cleavage.  They 
minimize  or  ignore  the  equally  important  blowpipe  or  chemical 
properties,  which  are  usually  quite  easily  ascertained,  and  as  a  rule, 
with  somewhat  greater  certainty  by  the  average  student  of  min- 

1  Books  on  Determinative  Mineralogy  are : 
Determinative  Mineralogy  and  Blowpipe  Analysis,  by  G.  J.  Brush  and  S.  L. 

Penfield  (most  complete  work  of  its  kind).     John  Wiley  &  Sons,  Inc. 
Determinative  Mineralogy,  by  A.  S.  Eakle.     John  Wiley  &  Sons,  Inc.     (By 

Physical  Properties.) 
Tables  for  the  Determination  of  Minerals,  by  P.  Frazer  and  A.  P.  Brown. 

J.  B.  Lippincott  Co. 

Most  of  the  Descriptive  texts  listed  above  contain  more  or  less  extensive 
determinative  tables. 

For  the  determination  of  opaque  minerals  by  means  of  the  reflecting 
microscope : 
Microscopic  Examination  of  Ore  Minerals,  by  W.  Myron  Davy  and  C.  M. 

Farnham.     McGraw-Hill  Book  Co.,  Inc. 

For  the  Determination  of  Minerals  with  the  polarizing  microscope: 
Determination  of  the  Rock-forming  Minerals,  by  Albert  Johannsen.     John 

Wiley  &  Sons,  Inc. 
Petrographic  Methods,  Part  II,  by  Dr.  E.  Weinschenk,  translated  by  R.  W. 

Clark.     McGraw-Hill  Book  Co.,  Inc. 
Elements  of  Optical  Mineralogy,  etc.,  by  N.  H;  and  A.  N.  Winchell.     D.  Van 

Nostrand  Co. 


THE  DETERMINATION  OF  MINERALS         91 

erals.  This  is  particularly  true  with  the  run  of  ordinary  mineral 
material  as  it  comes  from  the  mineral  deposits,  and  with  such  the 
purely  physical  determinations  commonly  lead  to  inconclusive 
or  erroneous  results.  They  are  perhaps,  useful  as  a  means  of 
acquainting  students  with  minerals  when  carefully  selected 
material  is  given  them,  and  where  there  is  plenty  of  time  for  such 
methods  of  instruction. 

The  second  type,  lays  the  first  and  main  emphasis  on  the 
diagnostic  value  of  blowpipe  and  chemical  properties,  and  uses 
the  physical  properties  for  making  the  final  distinctions  between 
chemically  similar  minerals.  This  form  of  table  gives,  in  general, 
more  reliable  results  than  the  first  type.  The  objection  to  it  is 
that  in  many  instances  it  subordinates  obvious,  or  easily  determin- 
able  physical  properties,  which  if  used  first  as  a  means  of  differ- 
entiation, might  render  very  simple  and  rapid  a  determination 
that  otherwise  is  long  and  tedious. 

The  third  type  aims  to  give  appropriate  weight  to  both  kinds 
of  properties  as  occasion  arises.  The  table  which  follows  (III)  is 
of  this  type.  In  it  are  listed  the  common  and  important  mineral 
species.  The  rarer  species  and  subordinate  varieties  are  not 
listed  in  many  cases,  but  references  are  given  to  the  more  com- 
prehensive tables  of  Brush  and  Penfield.  Indeed  with  the  majority 
of  minerals  listed  it  is  expected  that  a  descriptive  text  will  be 
consulted  for  final  confirmation,  for  only  by  so  doing  is  it  possible 
to  avoid  the  chance  of  serious  error  in  determination. 

The  following  observations  should  be  carefully  heeded  by 
the  student  of  mineralogy.  The  first  thing  to  do  in  determining 
a  mineral  is  to  examine  it  thoroughly  with  the  eye  alone  and  with 
a  pocket  lens.1 

This  examination  should  furnish  information  regarding  such 
matters  as  color,  structure,  crystallization  and  cleavage,  whether 
the  material  appears  to  consist  of  one  substance  or  more  than  one, 
and,  if  the  latter,  what  relation  the  different  ones  have  to  each 
other  as  regards  occurrence. 

1  A  lens  with  a  flat  field  and  of  about  one  inch  focus  is  recommended. 
For  fine-texture  material  a  simple  binocular  microscope  is  most  useful. 


92  DETERMINATIVE  MINERALOGY 

The  hardness  and  streak  may  then  be  tested  for. 

A  small  fragment  should  next  be  tested  B.B.  first  in  the 
forceps,  and  then  alone  on  charcoal,  and  results  noted.  Further 
tests  with  closed  and  open  tubes,  or  with  beads,  or  acids,  may 
next  be  carried  out,  but,  in  general,  time  may  be  saved,  and  the 
final  result  reached  quite  as  quickly,  and  more  safely,  by  referring 
to  the  determinative  scheme  as  soon  as  the  forcep  and  char  coal  tests 
B.B.  have  been  carried  out.  If,  however,  some  very  distinctive 
crystal  form  or  cleavage  can  be  clearly  and  certainly  made  out, 
reference  to  Tables  I  or  II  may  be  made  at  once,  although  in  general 
confirmatory  tests  have  to  be  made  by  beginners,  and  not  much 
time,  if  any,  is  gained  in  this  way. 

The  same  may  be  said  regarding  a  striking  color,  streak,  or 
structure,  and,  if  such  exist,  use  may  be  made  of  some  of  the  one 
tables  which  are  to  be  found  in  most  of  the  textbooks.  In  the 
writer's  experience,  however,  if  a  reliable  and  speedy  deter- 
mination is  desired,  the  most  satisfactory  procedure  is  to  follow 
out  Table  III  with  later  reference  (if  necessary)  to  Brush  & 
Penfield's  standard  work,  a  copy  of  which  should  always  be 
available. 

In  using  Table  III  it  will  be  noted  by  an  inspection  of  the 
"  Key  "  that  the  first  differentiation  is  made  on  the  basis  of  the 
character  of  the  streak.  Division  A  contains  those  minerals 
which  yield  black  or  dark  colored  streaks.  Division  B  contains 
those  with  white  or  light  colored  streaks.  The  few  minerals 
with  streaks  intermediate  between  light  and  dark  are  listed  under 
both  divisions. 

The  term  Streak  is  here  used  to  designate  the  color  of  the 
very  fine  powder.  The  streak  may  usually  be  obtained  by 
rubbing  the  mineral  on  a  piece  of  white  unglazed  porcelain  or 
white  whetstone  (Arkansas  Stone)  and  noting  the  color  of  the 
finely  powdered  material  left  on  the  plate.  A  good-sized  streak 
should  always  be  made  when  possible  so  that  it  can  be  clearly  seen. 
It  is  always  well  to  look  at  it  through  a  lens  also.  Where  very 
hard  minerals  are  being  studied,  which  scratch  the  streak-plate, 
small  fragments  should  be  powdered  very  fine,  and  the  color  of 


THE  DETERMINATION  OF  MINERALS  93 

the  powder  noted.  The  powder,  if  at  all  dark,  should  be  rubbed 
out  thin  on  a  piece  of  white  paper  to  bring  out  the  color. 

Many  minerals  are  metallic  in  character  and  these,  like  the 
common  metals,  are  opaque  to  light  and  yield  a  streak  which  is 
either  black  or  dark.  If  the  mineral  is  soft,  the  streak  will  often 
show  a  distinct  coloration,  perhaps  grayish  or  yellowish  (galena 
or  chalcopyrite  for  example),  and  possess  a  metallic  sheen.  This 
appearance  is  best  seen  if  the  streak  is  viewed  at  an  angle.  If 
viewed  directly  the  same  streak  may  appear  black  or  nearly  so. 
The  streak  should  always  be  examined  in  both  ways,  and  it  should 
be  noted  that  some  of  the  discrepancies  in  the  statements  regard- 
ing the  color  of  particular  streaks  in  different  textbooks,  are  due, 
in  part  at  least,  to  these  different  ways  of  viewing  the  streak. 

Minerals  yielding  such  dark  or  metallic  streaks  are  quite 
generally  spoken  of  as  having  a  Metallic  luster,  even  when  the 
mineral  itself  is  dull  in  appearance  and  does  not  suggest  what  is 
ordinarily  thought  of  as  a  metallic  appearance. 

Minerals  which  show  a  dark  brownish  or  reddish,  or  other 
colored  streak  are  somewhat  transparent  to  certain  wave  lengths 
of  ordinary  light,  and  such  are  often  referred  to  as  being  of  sub- 
metallic  luster. 

The  minerals  which  yield  white  or  light  colored  streaks  are 
transparent  to  light,  at  least  in  thin  pieces,  and  seldom  suggest 
anything  metallic  by  their  appearance,  though  many  of  them  are 
highly  lustrous,  and  may  be  dark  colored  in  the  specimen.  They 
are  often  referred  to  as  of  non-metallic  luster,  and  may  in  addition 
be  described  as  of  adamantine,  vitreous,  or  other  luster,  according 
to  their  appearance.  For  a  description  of  these  lusters,  as  well 
as  of  color,  a  descriptive  textbook  should  be  consulted. 

The  subdivisions  in  the  table  are  made  on  the  basis  of  the 
mineral's  behavior  when  heated  B.B.  on  charcoal  in  Division  I, 
and  on  the  behavior  in  the  forceps,  or  on  charcoal  B.B.,  in  Divi- 
sion II. 

Inspection  of  the  "  key,"  and  the  succeeding  tables,  will 
make  it  clear  as  to  how  further  differentiation  is  effected. 

In  using  the  tables  it  is  necessary  to  work  from  the  beginning 


94  DETERMINATIVE  MINERALOGY 

of  the  table  eliminating  each  division  successively.  The  whole 
value  of  the  order  of  arrangement  is  lost  if  this  is  not  done.  For 
example,  a  certain  mineral,  cryolite,  having  a  white  streak,  and 
fusing  easily  to  a  white  enamel  is  not  found  in  Division  II,  Sub- 
division D,  Section  b,  because  it  not  only  fuses  as  stated,  but 
gives  an  alkaline  reaction  and  falls  therefore,  in  the  preceding 
Subdivision  C,  Section  6.  So,  unless  each  division,  subdivision, 
and  section  is  eliminated  in  order,  the  one  containing  the  mineral 
sought  for  may  be  passed  by,  and  no  determination,  or  a  wrong 
one,  made. 

It  is  perhaps  desirable  to  point  out  here,  that  where  a  mineral 
cannot  be  wholly  freed  from  contaminating  substances,  or  where 
isomorphous  mixtures  are  being  examined,  some  departure  from 
the  behavior  of  the  ideally  pure  mineral  is  to  be  expected  and  must 
be  allowed  for  where  possible.  Thus  in  certain  Tetrahedrites 
(Division  I,  Subdivision  A,  Section  6)  a  little  arsenic  may  be 
present  with  the  antimony  and  evidences  of  arsenic  may  appear 
during  heating  B.B.  on  charcoal.  The  main  reaction  is,  however, 
for  antimony,  and  this  fact  should  be  used  in  following  out  the 
determination.  Or  again,  in  Division  II,  Subdivision  D,  Section 
6,  the  mineral  prehnite,  when  pure,  fuses  to  a  white  glass,  but  if, 
as  is  often  the  case,  a  little  iron  oxide,  or  other  iron  mineral  is 
present,  a  yellowish  or  brownish  glass  or  slag  is  obtained.  Pro- 
vision is  made  in  the  tables  for  such  irregularities  where  possible, 
but  it  is  well  to  keep  it  in  mind  that  due  allowance  must  often  be 
made  for  admixed  material. 

The  determination  of  fine-grained  minerals  where  several  may 
be  present  together,  or  of  coarser  material  which  may  contain 
inclusions  of  different  nature  from  the  main  mass,  necessarily 
presents  difficulties  and  seriously  limits,  or  restricts,  the  appli- 
cation of  the  methods  here  elaborated.  The  student  must  realize, 
as  of  course  the  experienced  mineralogist  does,  that  in  very  many 
instances  examination  by  other  methods  must  be  resorted  to,  to 
supplement  and  confirm  conclusions  reached  by  the  use  of  a 
table  like  the  present  one.  With  the  metallic  minerals  a  study 
of  polished  surfaces  under  the  microscope  is  of  the  greatest  service. 


THE  DETERMINATION  OF  MINERALS  95 

By  this  method  of  examination  a  variety  of  chemical,  and  some 
physical  tests,  can  be  applied  to  very  small  grains  in  a  mixture, 
and  distinctions  of  color  and  structure  can  be  noted,  that  wholly 
escape  the  eye,  unaided  by  the  microscope.  Often  what  appears 
to  be  homogeneous  material  is  found  to  be  in  reality  a  mixture. 
Examination  by  such  means  is  coming  increasingly  into  use. 
With  transparent  minerals,  examination  with  the  polarizing 
microscope  is  the  court  of  last  resort,  and  in  fact,  with  silicate 
minerals,  particularly  as  they  occur  in  the  fine-grained  or  dense 
rocks,  it  is  the  only  method  of  examination  capable  of  yielding 
the  information  desired.  The  minerals  are  examined  in  the  form 
of  fine  powders,  or  in  carefully  cut  thin  slices,  their  optical 
properties  determined,  and  their  structural  relations  ascer- 
tained. 

No  attempt  has  been  made  to  make  this  table  exhaustive. 
Many  rare  species  are  omitted.  For  some  of  these,  reference  is 
made  to  Brush  and  Penfield's  "  Determinative  Mineralogy,"  but 
even  here  there  are  now  a  good  many  omissions  of  recently 
described  species.  If,  in  the  process  of  determining  a  mineral,  a 
careful  study  of  the  minerals  listed  in  the  final  group  where  the 
mineral  in  question  falls,  shows  that  it  does  not  correspond 
entirely  with  the  minerals  listed  there,  the  appropriate  place  in 
Brush  and  Penfield's  tables  can  easily  be  found,  and  if  it  is  not 
finally  located  there,  then  enough  data  will  have  been  collected 
so  that  with  its  help,  the  mineral  may  be  located  in  Dana's 
"  System  of  Mineralogy,"  or  in  some  of  the  several  appendices  to 
that  work,  or,  in  some  one  of  the  summaries  of  newly  described 
minerals  to  be  found  in  recent  numbers  of  the  journals  devoted 
to  mineralogy. 

It  will  perhaps  be  evident  from  what  has  been  said  that  to 
determine  mineral  material  is  an  art  that  requires  no  little  knowl- 
edge and  skill,  good  powers  of  observation,  and  the  ability  to 
draw  conclusions  correctly  from  observed  facts. 

No  detailed  description  of  the  various  structures  that  char- 
acterize minerals  will  be  entered  into  here  inasmuch  as  they  are 
sufficiently  described  in  the  standard  descriptive  textbooks,  and 


96  DETERMINATIVE  MINERALOGY 

reference  may  be  made  to  these.  A  few  special  remarks  will, 
however,  be  made  regarding  cleavage  and  hardness. 

Cleavage. — By  the  term  cleavage,  as  applied  to  minerals,  is 
meant  the  breaking  or  splitting,  under  the  action  of  a  blow  or 
strain,  along  one  or  more  directions  which  are  parallel  to  definite 
crystal  planes.  These  planes  are  directions  of  marked  weakness 
in  the  crystal  structure  and  usually  follow  those  directions  in  the 
crystal  which  may  be  indicated  by  simple  index  relations  such  as 
the  cube  face,  (100),  a  prism,  (110),  or  a  pinacoid  (010).  Where 
the  cleavage  is  perfect,  plane  reflecting  surfaces  result. 

In  a  specimen  in  which  the  individual  crystals  are  of  fair  size, 
if  it  is  broken  carefully,  it  is  sometimes  possible,  particularly  if  a 
lens  or  microscope  is  used,  to  pick  out  and  identify  definite 
cleavage  forms,  for  example,  cubes  of  galena,  rhombohedrons  of 
calcite,  or  rhombic  plates  of  barite.  Again,  if  only  one  or  two 
cleavage  directions  exist,  the  relation  which  these  bear  to  the 
natural  crystal  form  may  be  ascertained.  In  general  the  pres- 
ence of  cleavage  in  a  granular,  more  or  less  compact  aggregate  of 
crystals,  is  indicated  on  a  broken  surface  by  many  reflecting  planes 
at  various  inclinations  which  make  the  surface  appear  bright, 
particularly  if  it  be  turned  at  various  angles  to  a  source  of 
light.  Very  minute  crystalline  structures  can  often  be  detected, 
if  a  lens  or  microscope  is  used,  by  noting  the  presence  of  reflecting 
planes  (very  fine  granular  galena  or  sphalerite  for  example),  even 
though  the  precise  nature  of  the  cleavage  cannot  be  told. 

As  some  minerals  possess  no,  or  only  very  poor,  cleavage,  the 
absence  of  evident  cleavage  should  not  be  taken  to  mean  the 
absence  of  crystalline  structure.  Almost  all  minerals  sometimes 
occur  in  massive  and  apparently  noncrystalline  form.  Amorph- 
ous materials  never  show  any  natural  cleavage. 

In  the  tables,  the  system  of  crystallization  and  the  cleavage 
are  indicated  by  suitable  abbreviated  symbols,  but  these  are 
given  only  in  cases  where  it  is  believed  that  they  are  likely  to  be 
of  practical  value  in  identifying  the  mineral. 

Hardness. — By  the  term  hardness,  as  applied  to  minerals,  is 
meant  the  relative  resistance  to  abrasion,  or  scratching,  offered 


THE  DETERMINATION  OF  MINERALS        97 

by  a  smooth  surface  (preferably  a  smooth,  natural  crystal  surface). 
The  standards  of  comparison  are  certain  substances  which  long 
experience  has  shown  to  be  suitable  for  this  purpose.  Taken 
together  they  form  a  series  of  ten  steps  of  differing  degrees  of 
hardness  and  are  known  as  the  Hardness  Scale.  It  is  as  follows: 

No.  1.  Talc  No.    6.  Orthoclase 

2.  Gypsum  7.  Quartz 

3.  Calcite  8.  Topaz 

4.  Fluorite  9.  Corundum 

5.  Apatite  10.  Diamond 

The  scale  is  entirely  arbitrary :  there  is  not  even  an  approximation 
to  uniformity  in  the  differences  of  hardness  between  members  of 
the  scale.  Indeed,  there  is  evidence  to  show  that  the  interval 
between  9  and  10  is  probably  greater  than  between  1  and  9. 
However,  the  scale  is  of  much  practical  value. 

In  actual  practice  for  ordinary  work  a  shorter  and  simpler 
scale  is  often  used,  viz., 

The  finger-nail  about  2.5 
Steel  about  5.5 

or  glass  5.5  to  6 

Quartz  7 

Any  mineral  that  can  be  scratched  with  the  finger-nail  may  be 
classed  as  very  soft;  one  that  can  be  scratched  by  steel,  but  not 
with  the  nail,  as  soft;  one  scratched  by  quartz,  but  not  by  steel, 
as  hard,  and  one  not  scratched  by  quartz,  as  very  hard. 

In  testing  for  hardness,  as  smooth  a  surface  as  possible  should 
be  chosen,  a  good  crystal  face  being  the  best  surface.  It  is  then 
ascertained  by  trial  which  mineral  of  the  hardness  scale  will  just 
clearly  scratch  the  surface  which  is  being  tested.  It  is  generally 
well  to  reverse  the  process  and  test  surfaces  of  the  hardness 
specimens  with  a  corner  or  edge  of  the  mineral  whose  hardness  is 
to  be  found.  Too  much  force  should  not  be  used,  but  a  steady 
firm  pressure  should  be  exerted  in  drawing  the  one  across  the 
surface  of  the  other.  In  attempting  to  scratch  an  irregular  and 
rough  surface,  particularly  a  granular  one,  small  fragments  or 


98  DETERMINATIVE  MINERALOGY 

grains  may  be  broken  out  and  crushed,  often  giving  the  impression 
that  the  material  is  softer  than  the  testing  edge,  whereas  it  may 
have  a  true  hardness  which  is  greater.  This  can  generally  be 
told  if  a  smooth  surface  of  known  hardness  is  carefully  rubbed 
with  the  mineral  (or  with  grains  broken  from  it),  and  the  surface 
examined  with  a  lens  for  scratches. 

In  using  a  knife  blade  or  other  steel  tool  it  will  sometimes  be 
found  that  it  will  scratch,  or  apparently  scratch,  a  surface,  while 
the  same  surface  will  scratch  ordinary  glass,  and  the  latter  is 
usually  unscratched  by  steel.  This  illustrates  again  the  fact, 
that  hardness  testing  is  far  from  an  accurate  method  of  testing. 
It  is,  nevertheless,  a  most  useful  one  in  practice. 

There  is  sometimes  a  noticeable  difference  of  hardness  in  differ- 
ent directions  in  crystals  (example,  cyanite). 

Specific  Gravity.  —  The  specific  gravity  of  a  pure,  homoge- 
neous mineral  material  is  a  physical  constant  that  can  often  be 
determined  quickly  and  quite  accurately,  and  is,  therefore,  one 
of  considerable  importance  in  the  determination  of  minerals. 
When  fragments,  or  crystals,  weighing  a  gram  or  more,  and  of 
undoubted  homogeneity,  are  available,  a  sufficiently  good  deter- 
mination of  the  specific  gravity  can  be  made  with  one  of  the 
simple  forms  of  specific  gravity  balances  described  in  the  text- 
books of  mineralogy. 

Such  determinations  are  particularly  useful  when  it  is  impor- 
tant, for  any  reason,  not  to  impair  or  destroy  the  specimen. 
They  are  often  useful  as  a  means  of  confirming  mineral  identi- 
fications worked  out  by  other  methods. 

In  general,  until  the  student  has  acquired  considerable  experi- 
ence in  mineral  determination,  he  should  seek  the  advice  of 
his  instructor  before  carrying  out  a  specific  gravity  determina- 
tion. Many  useless  and  even  misleading  determinations  may  be 
made,  and  time  wasted,  unless  due  care  is  exercised  regarding 
the  character  of  the  material  and  the  particular  method  to  be 
used. 

For  a  description  of  the  methods  and  apparatus  used  in  deter- 
mining the  specific  gravity,  reference  may  be  made  to  one  of 


THE  DETERMINATION  OF  MINERALS  99 

the  standard  text-books  on  mineralogy,  particularly  to  Brush  and 
Penfield's  treatise,  p.  232.  For  more  refined  methods,  one  of  the 
more  extended  texts  on  experimental  physics  should  be  con- 
sulted. 

Attention  is  here  especially  directed  to  the  fact  that  certain 
liquids  of  high  density  ("heavy  solutions")  can  be  used  to  advan- 
tage in  many  instances  for  the  determination  of  the  specific  gravity 
of  minerals.  The  liquids  are  adjusted  by  dilution  until  the  min- 
eral grains,  whose  specific  gravity  is  to  be  determined,  are  just 
suspended,  (neither  float  nor  sink),  and  then  the  specific  gravity 
of  the  liquid,  which  is  then  the  same  as  that  of  the  mineral,  is 
determined  with  a  pycnometer. 

The  same  liquids  are  often  employed  to  separate  minerals 
of  different  densities  from  one  another.  See  B.  &  P.,  p.  238. 

Magnetic  Separation  of  Minerals.  —  Mixtures  of  two  or 
more  minerals  may  sometimes  be  crushed  to  a  fine  sand  and 
separated  by  means  of  their  different  magnetic  susceptibilities. 
A  powerful  electro-magnet,  the  strength  of  which  can  be  regu- 
lated, is  passed  over  the  mineral  sand  spread  out  thinly  on  a 
glass  plate.  Those  grains  which  are  attracted  with  sufficient 
force  are  picked  up  and  thus  separated  from  the  remainder. 
Magnetite  may  be  easily  and  completely  removed  from  a  sample, 
using  a  very  weak  magnetic  flux.  Ilmenite,  hematite  and  chromite 
may  be  picked  by  a  stronger  flux  and  thus  separated  from  iron- 
bearing  silicates  such  as  garnet,  hornblende,  etc.  Ihe  latter  can 
be  then  separated  from  quartz  and  other  non-magnetic  min- 
erals. The  non-magnetic  residue  from  such  a  treatment  may 
then  be  further  broken  up  into  fractions  by  means  of  "heavy- 
solutions."  The  magnetic  separation  has  proved  very  useful 
in  the  examination  of  natural  sands  and  crushed  mill-products. 


100 


DETERMINATIVE  MINERALOGY 


TABLE  I 
COMMON  MINERALS  SHOWING  VERY  DISTINCT  OR  PERFECT  CLEAVAGE 


Character  of  Cleavage. 

Mineral. 

Dark  Streak. 
(Metallic  Luster.) 

Light  colored  or  white 
Streak. 
(Non-metallic     Lus- 
ter.) 

Cubic.  I.  Cleaves  in  three  rect- 
angular directions. 

Galena. 

Halite. 

Sylvite. 
Periclase. 

Pseudo-Cubic.    Not  Isometric. 

Corundum    R. 
Anhydrite.     O. 
Cryolite.     M. 

Octahedral.  I.  Cleaves  in  four 
equally  inclined  directions. 

Magnetite  (parting). 

Fluorite. 
Diamond. 

Dodecahedral.  I.  Cleaves  in 
six  directions  making  angles 
of  60°. 

Sphalerite. 
(Black  color.) 

Sphalerite. 

Rhombohedral.  Cleaves  in 
three  equally  inclined  direc- 
tions. 

Calcite. 
Dolomite. 
Magnesite. 
Rhodochrosite. 
Siderite. 
Ankerite. 
Corundum      (parting, 
nearly  cubical). 

Parallel  to  two  inclined  Pris- 
matic directions,  and  another 
at  right  angles  (Basal). 

Barite.     ^  Rhombic 
Celestite  j  fragments 

THE  DETERMINATION  OF  MINERALS 


TABLE  I— (Continued) 


Parallel  to  two  inclined  pris- 
matic directions. 

Enargite. 
Arsenopyrite. 

Amphiboles.      M. 
Cleavage  angle  124°. 

Parallel  to  two  directions  at 
right  angles. 

The  Feldspars.      (|| 
to  001  and  010.) 

Parallel  to  one  direction. 

Graphite  (basal). 
Molybdenite  (basal). 
Jamesonite  (basal). 
Stibnite  (|l  to  010). 
Bismuthinite      (||     to 
010). 
Wolframite  (||  to  010). 

The  Micas  (Basal). 
The  Chlorites  (Basal). 
The    Brittle    Micas 
(Basal). 
Talc  (Basal). 
Topaz  (Basal). 
Apophyllite  (Basal). 
Pyroxene    (Basal 
parting). 

102          DETERMINATIVE  MINERALOGY 

TABLE  II 

COMMON  MINERALS  WHICH  OFTEN  SHOW  EASILY  RECOGNIZED  OR  DETER- 
MINABLE  CRYSTAL  FORMS 

A.  ISOMETRIC  CRYSTALS. 

CUBES,  or  slightly  modified  cubes.     Metallic  Luster. — Galena.   Pyrite. 

Cobaltite.     Smaltite. 
Non-metallic. — Fluorite.     Halite.      Sylvite.     Boracite.      Cerargyrite. 

Periclase. 
OCTAHEDRONS,  Metallic. — Magnetite.     Chromite.     Franklinite.     Less 

commonly  Pyrite.     Galena.     Perovskite. 
Non-metallic. — Spinel.     Cuprite.     Diamond. 
DODECAHEDRONS. — Magnetite  (metallic).     Garnet.     Cuprite. 
TRAPEZOHEDRONS. — Garnet.     Leucite.     Analcite. 
PYRITOHEDRONS. — Pyrite.     Cobaltite. 
TETRAHEDRONS. — Tetrahedrite     (metallic).       Sphalerite.       Boracite. 

Diamond. 

B.  TETRAGONAL. 

SQUARE  PYRAMIDS. — Zircon.     Wulfenite.     Vesuvianite.     Octahedrite. 

Xenotime. 

SQUARE  PRISMS. — Zircon.     Vesuvianite.      Scapolite.     Apophyllite. 
SQUARE  PLATES. — Wulfenite.     Torbenite.     Apophyllite. 

C.  HEXAGONAL. 

HEXAGONAL  PYRAMIDS. — Quartz.  Apatite.  Corundum.  (Pseudo-hex- 
agonal).— Witherite.  Cerussite. 

HEXAGONAL  PRISMS. — Quartz.  Beryl.  Calcite.  Apatite.  Pyromor- 
phite.  Vanadinite.  Corundum.  Pseudo-hexagonal. — Aragonite. 
Strontianite.  Amphibole. 

HEXAGONAL  PLATES. — Graphite.    Molybdenite.   Pseudo-hex. — Micas. 

TRIGONAL  PRISMS. — Tourmaline. 

RHOMBOHEDRONS. — Calcite.  Dolomite.  Siderite.  Ankerite.  Rho- 
dochrosite.  Chabazite. 

SCALENOHEDRONS. Calcite.       PfOUStite. 

D.  OTHER  SYSTEMS. 

PRISMATIC  CRYSTALS. — (Metallic).  Stibnite,  O.  Manganite,  O.  Arsen- 
opyrite,  O.  Pyrolusite,  O.  Enargite,  O.  Goethite,  O.  Wolfra- 
mite, M. 

Non-metallic. — Topaz,  O.  Sillimanite,  O.  Barite,  O.  Celestite,  O. 
Staurolite,  O.  Amphiboles,  M.  Pyroxenes,  M.  Epidote,  M. 

TABULAR  HABIT. — Barite,  O.  Celestite,  O.  Calamine  (U.  in  radiating 
groups  or  crusts),  O. 

TYPICAL  MONOCLINIC  HABIT. — Orthoclase.     Pyroxene.     Amphibole. 

•  Titanite.     Gypsum.     Microcline,  Trie.     Pseudo-monoclinic. 

TRICLINIC  HABIT. — Axinite.     Chalcanthite. 


THE  DETERMINATION  OF  MINERALS  103 


GENERAL  TABLE,  III 

FOR  THE  DETERMINATION  OF  MINERALS  BY  MEANS  OF  BLOWPIPE  REAC- 
TIONS, SIMPLE  CHEMICAL  AND  PHYSICAL  EXAMINATION 

Key 

Division  I.     The  mineral  yields  a  black  or  dark-colored  or  metallic  streak 

(metallic  or  submetallic  luster). 

SUBDIVISION  A.  The  mineral  gives  a  sublimate  when  heated  alone  on  char- 
coal B.B. 

Section  a.  Gives  a  sublimate  of  arsenic  oxide  (see  p.  25) 105 

Section  6.  Gives  a  sublimate  of  antimony  oxide  (see  p.  23) 107 

Section  c.  Gives  a  sublimate  of  antimony  oxide  and  one  of  lead  or 
bismuth  oxide  (see  pp.  23,  44  and  29;   confirm  Sb,  by 

test,  4,  p.  24) 108 

Section  d.  Gives  a  sublimate  of  lead  or  bismuth  oxide  (see  1,  44  and  1, 

p.  29 109 

Section  e.  Gives  a  sublimate  of  zinc,  tin,  or  molybdenum  oxide 

(see  pp.  75,  69,  and  49) 110 

Section  f.  Gives  a  sublimate  of  tellurium  oxide  (see  4,  p.  68). .-.  .  .    110 

Section  g.  Gives  a  sublimate  of  selenium  oxide  (see  p.  57) Ill 

SUBDIVISION  B.  The  mineral  fuses  in  the  forceps  or  on  charcoal  B.B. 

but  gives  no  sublimate   Ill 

SUBDIVISION  C.  The  mineral  is  infusible  in  the  forceps  or  on  charcoal 

B.B.  and  yields  no  sublimate 114 

Division  II.     The  mineral  yields  a  white  or  light-colored  streak  (non-metallic 

luster) . 
SUBDIVISION  A.  The  minerals  are  soluble  in  water  (have  a  saline  bitter 

or  astringent  taste) 119 

SUBDIVISION  B.  Heated  intensely  alone  in  the  C.T.  or  on  charcoal  (and 
sometimes  by  both  methods)  the  mineral  is  partially 
or  wholly  volatile,  or  yields  a  sublimate  other  than 
water;  most  of  them  fuse. 

Section  a.  Readily  and  completely  volatile 120 

Section  b.  Yield  a  sublimate  of  arsenic  oxide 121 

Sections  c,  d,  e.  Yield   a   sublimate    of    lead     (c),   bismuth     (d),  anti- 
mony    (e)    oxide 122-3 

Section  f,  g.  Yield  a  sublimate  of  zinc     (/),   or   molybdenum     (g) 

oxide 124 

Section  h.  Fuse  easily  and  yield  a  silver  globule .* . .   124 


104  DETERMINATIVE  MINERALOGY 

SUBDIVISION  C.  The  mineral  fuses,  B.B.  but  is  non-volatile  and  yields 

no  sublimate  (except  sometimes  water)  either  in  the 

C.T.  or  on  charcoal. 
Section  a.  The  mineral  turns,  or  remains,  black  on  fusion  B.B. 

and  when  cold  is  attracted  by  the  magnet 125 

Section  b.   After  fusion  B.B.  the  mineral  yields  an  alkaline  reaction 

on  moistened  turmeric  or  litmus  paper  1 128 

SUBDIVISION  D.  The  mineral  fuses  in  the  forceps  B.B.  but  does  not  react 

as  under  A,  B  and  C. 
Section  a.  The  mineral  fuses  to  a  colorless  glass 129 

Section  b.  The  mineral  fuses  in  the  forceps  to  a  white  glass,  enamel 

or  slag2 132 

Section  c.  The  mineral  fuses  to  colored  or  black  glass,  enamel  or 

slag2 137 

SUBDIVISION  E.  The  mineral  is  infusible  alone,  B.B. 

Section  a.  The  mineral  is  white,  or  becomes  so  upon  ignition  B.B. 
The  powder  moistened  with  cobalt  nitrate  solution  and 
then  intensely  ignited  in  charcoal  B.B.  assumes  a  fine 

blue  color 143 

Section  b,  etc.  Minerals  not  previously  included 146 


APPENDIX  TO  KEY,  TABLE  III 

When  heated  B.B.  the  mineral  burns  and  may  give  an  empyreumatic 
order — carbon  and  hydrocarbons.  In  some  cases  heated  in  the  C.T.  gases, 
tars  and  pitchy  materials  are  sublimed. 

Black  or  brownish-black,  brittle Coals 

Black  or  brownish,  of  tar-like  consistency Bitumens 

Yellowish  to  brownish,  waxy Natural  waxes 

Yellowish  to  brownish,  brittle Ambers 

For  description  and  details  regarding  these  mineral  substances  see  Dana's 
"  System  of  Mineralogy,"  pp.  996-1024. 

1  The  absence  of  calcite  (see  test  B.  1,  p.  35)  should  be  assured,  as  small 
amounts  are  very  often  present  with  other  minerals  and  will  give  the  alkaline 
reaction. 

2  See  general  remarks,  p.  94,  and  note  that  slight  impurities  may  cause 
the  mineral  to  fuse  white  or  colored,  whereas  if  pure,  it  would  fall  in  either 
Section  a  or  6,  and  it  may  be  necessary  to  look  for  it  under  these  sections  also. 


THE  DETERMINATION  OF  MINERALS 


105 


Division  1.  Minerals  yielding  a  black  or  dark  colored  or 
metallic  streak.  (Metallic  or  submetallic  luster.) 

SUBDIVISION  A.  The  mineral  yields  a  sublimate  when  heated 
alone  B.B.  on  charcoal. 

Section  a.  The  mineral  yields  a  white,  very  volatile  sublimate 
of  arsenic  trioxide  (p.  25).  A  garlic-like  odor  is  often  obtained. 
Rarely  a  sublimate  of  antimony  or  lead  oxides  may  be  obtained. 


4J 

Wholly  volatile  B.B. 

Native     Arsenic.       U.     Botryoidal. 
H  =  2.5. 

l« 

Enargite,    Cu3AsS4.      O.      Cleavage 

O 
>> 

good.     Color  black. 

&  • 

Tennantite,  Cu8As2S7.     I.  U.  mass. 

»   T* 

-2     * 

Contain    copper   and  sul- 

May contain  antimony.   See  Tetra- 

£    ° 
""O   CO 

phur. 

hedrite  below.    The  streak  may  be 

08   -£ 

The  nitric  acid  solution  is 

reddish. 

11 

rendered  deep  blue  by  the 

Pearceite,  9(Ag,Cu)2S-As2S3.    R.  Sil- 

addition of  ammonia. 

ver  test. 

flj         ^ 

1    1 

For  a  few  very  rare  minerals  which 

s-§ 

II 

fall  here,  see  B.  &  P.,  p.  246. 

!S 

Sx 

Contain  lead  and  sulphur. 

For  a  few  very  rare  minerals  which 

"1 

Give  a  sublimate  of  lead 

fall  here,  see  B.  &  P.,  p.  246. 

0 

oxide  which  comes  later, 

H 

and   inside   that    of    the 

arsenic. 

Continued  on  next  page. 


106 


DETERMINATIVE  MINERALOGY 


Color  pale  copper-red. 

NICCOLITE,      NiAs.       U.     massive. 

Hardness  5  to  5.5. 

Wholly  volatile  B.B. 

Native  Arsenic,  As.      O.  U.  Botry- 

oidal. 

CO 

5 

IQ 

$ 

O 

Contain      Cobalt      (tests 
p.   37).     In   this   group 
small  amounts  of  Fe  and 

]  Pyritohedral 
Smaltite,  CoAs,     I.       {         f 

Cobaltite,  CoAsS.  I.  j    ^ 

"2 

Ni  may  be  isom.  with  Co. 

Glaucodot  (Co,Fe)AsS.     O. 

1 

For  other  rare  species  which  fall  here, 

see  B.  &  P.,  p.  246. 

1 

Contain  Nickel   (tests  p. 

Chloanthite,  NiAs2.     I. 

J 

50)  .     In  this  group  small 

Gersdorffite,  NiAsS.     I. 

M 

amounts  of  Co  and  Fe 

For  other  rare  species  which  fall  here, 

O 

may  be  isom.  w.  Ni. 

see  B.  &  P.,  p.  247. 

1 

W 

Contain    Iron.      Fuse   to 

ARSENOPYRITE,  FeAsS.    O.  civ. 

s" 

strongly  magnetic  glob- 

prism.     Crystals  common.      Also 

1 

ules. 

massive. 

.9 

Lollingite,  FeAs2.       \  „ 

T               -A     -n    A       f  Very  rare. 
Leucopynte,  tesAs-i.  j 

O 

* 

Contain  Platinum. 

Sperrylite,  PtAs2.  I.     Very  rare. 

03 

Contain  Copper.  The  min- 

Domeykite, Algodonite,  Whitney  ite, 

g 

erals  are  very  rare. 

C  Copper  arsenides. 

*0 

Mohawkite.  \  Mohawkite  contains 

g 

Co  and  Ni. 

p 

Some  of  these  are  mixtures. 

For  other  species,  see  B.  &  P.,  p.  246. 

THE  DETERMINATION  OF  MINERALS 


107 


I — A.  Section  b.  The  mineral  fuses  with  great  ease  (1-1.5), 
and  yields  a  dense  white  coating  of  oxide  of  antimony  on  char- 
coal (see  2,  p.  23,  confirm  by  4,  p.  24),  but  no  yellow  sublimate  of 
lead  or  bismuth  oxide.  If  doubtful  as  to  the  presence  of  latter, 
test  for  lead  and  bismuth,  test  2  or  3,  pp.  29,  30,  and  3  or  4,  pp. 
45,  46. 

Small  amounts  of  arsenic  maj7'  be  present  (isom.  w.  Sb)  so 
that  a  slight  garlic  odor  may  be  noted. 

Sulphur  is  present  in  most  of  the  minerals  of  this  section. 

Decomposed  with  cone.  HNOs,  they  yield  a  white  residue 
(p.  24).  For  t*he  most  part  they  are  quite  soft. 


Completely  volatile.     Color  tin-white 
or  lead-gray. 

STIBNITE,  Sb2S3.     0.     U.     prism, 
columnar,     bladed,     rarely     gran. 
Civ.  pine.  perf.     Marks  paper. 
Native  Antimony,  Sb.     R. 

React  for  silver.     Color  dark  red. 

Pyrargyrite,  Ag,SbS3.     R. 
(Ruby  silver  in  part.) 

React  for  Silver.   Color  gray  to  black, 
except  dyscrasite,  which  is  silver- 
white. 

Stephanite,  5Ag2S.Sb2S3. 
Miargyrite,  Ag2S.Sb2S3.         -\ 
Polyargyrite,  12Ag2S.Sb2S3.  }.  Rare. 
Dyscrasite,  Ag3Sb  ?.              } 

React  for  copper  and  cilvcr.     Color 
gray  to  black. 

Freibergite,  4(Cu,Ag)2S.Sb2S>     I. 
Polybasite,  9(Ag2,Cu)2S.Sb2S3.     R. 

React  for  copper,  color  gray  to  black. 

TETRAHEDRITE,       Essentially 
4Cu2S.Sb2S3.     I.  Tetrahedral  crys- 
tals, U.  massive. 
See  also  B.  &  P.,  p.  250. 

React  for  Iron  and  Nickel. 

For  very  rare  species,  see  B.  &  P., 
p.  250. 

108 


DETERMINATIVE  MINERALOGY 


I — A.  Section  c.  The  minerals  fuse  with  great  ease  (1-1.5) 
and  yield  a  dense  white  coating  of  oxide  of  antimony  on  charcoal 
B.B.  (2,  p.  23),  and  also  a  yellow  coating  of  lead  oxide  (1,  p.  44), 
rarely  of  bismuth  (1,  p.  29),  or  a  white  one  of  tin  (3,  p.  69),  nearer 
the  assay. 

All  of  the  minerals  react  for  sulphur  (test  2,  p.  65). 

A  little  arsenic  may  be  present  (isom.  w.  Sb)  so  that  a  slight 
garlic  odor  may  be  noticed. 

Confirmatory  test  for  Pb  (3,  p.  45),  for  Bi  (2,  p.  29). 

The  minerals  are  black,  or  some  shade  of  gray,  soft  (H  =  2-3.5) 
and  of  high  density  (Sp.  G.  =  5-6.5). 


Contain  Lead,  Antimony  and  Sulphur. 

Jamesonite  (Feather  ore),  essentially 
2PbS.     SbsSs.      U.      has   a   finely 
fibrous  structure. 
A  number  of  very  rare  minerals,  con- 
taining PbS  and  Sb2S3  in  varying 
proportions,  and  distinguished  by 
differences   in   physical   properties 
fall  here,  see  B.  &  P.,  p.  249. 

Contains  Copper. 

Bournonite,  2PbS.Cu2S.Sb2S3.      O. 

Contains  Bismuth. 

See  Brush  and  Penfield,  p.  260. 

Contain  Silver. 

For  several  rare  species,  see  B.  &  P., 
p.  249. 

Contain  Tin.     After  long  heating  in 
O.F.    leave    a   white    non-volatile 
oxide  (1,  p.  69).     Fused  with  char., 
and  Na2CO3,  give  globules  of  tin. 

Cylindrite,    J  PbS.SnS,.FeS.SbA,    in 
Franckeite,         ™rvmS  Proportions, 
l      Very  rare. 

THE  DETERMINATION  OF  MINERALS 


109 


I — A.  Section  d.  The  mineral  fuses  and  yields  a  yellowish 
coating  of  lead  or  bismuth  oxide.  (Confirm  by  tests,  2,  p.  29  and 
2  or  3,  pp.  29-30.)  The  minerals  with  two  exceptions  are  sulphides. 


Contain  lead,  but  no  bismuth. 


Contain  bismuth,  but  no  lead,  copper 
nor  silver. 


Contain  bismuth  and  copper  or  silver, 
but  no  lead. 


Contain  both  lead  and  bismuth. 


Small  amount  of  Cu  and  Ag  may  be 
isom.  with  Pb;  also  Sb  iso.  with  Bi. 
(Cylindrite  and  Franckeite,  1 — A, 
Section  c,  give  a  poor  Sb  test  and 
might  fall  here.) 


Native  Lead,  I. 

GALENITE   (galena),   PbS.     I.     In 

simple  Isom.  crystals,  also  coarse 

to  fine  granular. 

Civ.  cubical  perf.  Sp.  G.  7.6 

H  =  2.5-2.7. 


Native  Bismuth,  Bi.     R. 

Civ.  basal  and  rhomb,  perf. 
Bismuthinite,  Bi2S3.      O.      bladed  or 

prismatic  habit. 

Civ.  pine.  perf. 


The  minerals  are  very  rare. 
See  B.  &  P.,  p.  251. 


The  minerals  are  all  very  rare. 
See  B.  &  P.,  p.  251. 


The  minerals  are  all  very  rare. 
See  B.  &  P.,  p.  251. 


Some  tellurium  minerals,  containing  antimony  may  fall  here  also.     See 
beyond,  1— A.,  /,  p.  110. 


110 


DETERMINATIVE  MINERALOGY 


I — A.     Section  e.     The  mineral  yields  a  sublimate  of  zinc 
(1,  p.  75),  tin  (1,  p.  69),  or  molybdenum  (1,  p.  49),  oxide. 


Reacts  for  zinc.     H2S  with  HC1. 


Contains  molybdenum. 


Contains  tin.     B.B.  in  R.F.  becomes 
magnetic.     Reacts  for  copper. 


SPHALERITE  (Zn,Fe)S.     I.  perf. 
Civ.    in  six  directions    (dodecahe- 
dral).         Color    black    or    brown. 
Streak,     brown.     H  =  3.     Infusible 
or  nearly  so.     U.  granular. 


MOLYBDENITE  MoS2.  R.  Color 
bluish-gray;  streak  same  when 
heavy.  Foliated,  very  soft  (H  =  1). 
Civ.  basal,  perf.  Resembles  graph- 
ite. 


Stannite,  Cu2S.FeS.SnS2.  Color  steel- 
gray  with  yellowish  tarnish.  U. 
massive. 


I — A.  Section  f.  The  mineral  fuses  very  easily  (1-1.5). 
Yields  a  white  sublimate  of  Tellurium  oxide  B.B.  on  charcoal,  and 
U.  a  pale  bluish-green  flame  (4,  p.  68.  Confirm  by  test  1  or  3, 
p.  68).  All  the  minerals  of  this  group  are  of  rare  occurrence. 


Wholly  volatile  B.B. 

Native  Tellurium,  Te.     R. 
Civ.  prism,  perf. 
Coloradoite,  HgTe. 

Contain  Bismuth. 

Tetradymite,  Bi2Te3 
Civ.  basal  perf. 
See  also  B.  &  P.,  p 
minerals. 

to  2Bi2Te3.  Bi2S3. 
248  for  very  rare 

Contain  Lead. 

See  B.  &  P.,  p.  248. 

THE  DETERMINATION  OF  MINERALS 
I — A.     Section  f. — Continued. 


Ill 


Contain  silver  or  gold.     U.  both  to- 
gether.    Ag.  isom.  with  Au. 


Lead  or  silver-gray. 
Somewhat    sectile. 


Hessite,  Ag2Te. 
U.  massive. 
H=  2.5-3. 

Petzite  (Ag,Au)2Te.  Gray  to  black. 
Fine  granular  to  compact. 
H=  2.5-3. 

Sylvanite  (Au,Ag)Te2.   M.  Civ.  Pine. 
(010)    perf.     Steel-gray    to    silver- 
white,  inclining  to  yellow. 
H  =  1.5-2. 

Krennerite  (Au,Ag)Te2.  Prismatic, 
striated.  Silver-white  to  brass- 
yellow. 

Calaverite,  AuTe2.  Silver-white  to 
yellow.  Brittle.  H  =  2.5. 


Contains  nickel  or  copper.  Very  rare  minerals.  See  B.  &  P.,  p. 248. 

I — A.  Section  g.  The  mineral  yields  a  coating  of  Selenium 
oxide,  p.  57.  Gives  a  blue  flame  coloration  and  a  very  disagree- 
able odor. 

For  these  very  rare  minerals  see  Brush  and  Penfield,  p.  247. 

I.  SUBDIVISION  B.  The  mineral  fuses  B.B.,  but  yields  no 
coating. 


J-j 

°3 

Color   red.     Yield   a   cop- 

NATIVE COPPER,  Cu.     I.  Malle- 

2 

per  globule  easily 

able. 

b 

O 

B.B.  on  char. 

CUPRITE,  Cu2O.    I.  Simple  cryst. 

1 

Contain  no  S. 

forms,    also   fibrous   and   massive. 

1 

Brittle.     H  =  3.5-4. 

§H 

TJ" 

Reacts  for  copper  and  sul- 

BORNITE,   Cu5FeS4.     U.   massive. 

g 

phur.     Yield   sulphur  in 

Mag.   B.B.   in   R.F.     The  freshly 

.22 

the  C.T. 

broken  surface  is  reddish  bronze. 

to 

O 

The  old  surface  is  purplish  or  blue- 

'o 

o 

ish. 

1 

Covellite,  CuS.  Tabular  habit.  Soft. 

H 

H  =  1.5-2.     Color,  purplish-blue. 

Continued  on  next  page. 


112  DETERMINATIVE  MINERALOGY 

I — A.     Section  g. — Continued. 


3 
«  B 

02      <~{ 

«4H     J2* 

^3 
11 

+3 

^Q       CU 

?1 
*£ 
f  °- 

0.2" 

5T     -, 

¥g 

°J 

11 

°"a 
•s  " 

|| 

<o  g 

1 

Malleable,  insoluble  in  any 
single  acid. 

GOLD,  Au.  I.  Yellow  (Electrum, 
Au,Ag,  is  light  yellow). 

Hardness  greater  then  steel. 
Burns,   yielding  SO2. 
Abundant  S  in  C.T. 

PYRITE,    FeS2.     I.     Cryst.    cubes, 
pyritohedrons,   octahedrons.     Also 
mass.,  granular.     Light  brass-yel- 
low. 
MARCASITE,     FeS2.     O.     Cryst. 
and  mass.     Color  U.  paler  yellow 
than  pyrite. 

Hardness  less  than  steel. 
Reacts  for  copper  and 
iron  and  gives  S  in  the 
C.T. 

CHALCOPYRITE,  CuFeS2.     T. 
Crystals     tetrahedral     in     habit. 
Brass-yellow  color.     U.  massive. 

Reacts  for  nickel  (2,  p.  50). 

Millerite,    NiS.     (capillary    pyrite). 
Prismatic     to     hair-like     crystals, 
often  in  radiating  groups. 
Pentlandite   (Ni,Fe)S.     U.   massive. 
Yellowish-bronze    color.         Occurs 
with  Pyrrhotite. 

*:  °»  *-" 

CJ     V     O 

N  "s 
2  'o  -g 

^  ^  i 

IN 

.2   ^  tf 

S3_§  ^' 

-3    o  •$  rG 

^  M      J3* 
2(2  Jl 

Contains  only  Iron  and  sul- 
phur. U.  mag.  without 
heating. 

PYRRHOTITE,  FeS+XS.  U. 
massive.  Brownish-bronze  color. 
Gives  a  slight  sublimate  of  S.  hi  C.T. 

Reacts  for  nickel  (2,  p.  50). 

Pentlandite  (Ni,Fe)S.     See  above. 

Contains  copper  and  iron. 

Bornite,  see  above. 

Contains  silver  and  iron. 

Sternbergite,  AgFe2S3. 

THE  DETERMINATION  OF  MINERALS 


113 


I — A.     Section  g. — Continued. 


-s  ® 

to  '53 

3"! 

h. 

!it 

is-2 

Fuses  to  a  silver-white, 
malleable  globule. 

Native  Silver,  Ag.     I.     Malleable. 

Soft.  After  roasting  gives 
a  copper  globule  on  char. 

CHALCOCITE     (Copper     glance). 
Cu2S.     O.     U.  mass.     Black  tarn- 
ish.    Almost  sectile.     H  =  2.5-3. 
Stromeyerite  (Cu,Ag)2S.     H=  2.5-3. 

Contain  cobalt  or  nickel, 
and  often  iron. 

Linnaeite,  (Co,Ni)3S4.     I.    H  =  5-5.5 
Polydymite,  Ni4S8. 
For  other  species,  see  B.  &  P.,  p. 
252. 

The  color  is  black  or  brownish-black. 

Very  soft.  Sectile,  vis., 
cut  like  lead.  Fuse  easily. 
Yield  a  bright  silver  glo- 
bule on  char. 

Argentite  (Silver  glance),  Ag2S.     I. 
Acanthite,  A&S.     O. 

Yields  a  copper  globule  on 
char. 

CHALCOCITE,    Cu2S.         (Copper 
glance).    O.     U.  massive.     Almost 
sectile.     Fresh  surface  is  dark  gray. 
H  =  2.5-3. 
Tenorite     (melaconite),     CuO.      U. 
massive.     Often  impure. 

The  streak  of  these  minerals 
is  quite  dark  (grayish  or 
greenish),    although    not 
metallic. 
Fuse    with    intumescence. 
Ilvaite  yields  a  strongly 
magnetite    black  globule 
B.B.     in    R.F.     Allanite 
U.,  and  Tourmaline  some 
times,  yields  a  mag.  glo- 
bule. 

TOURMALINE,    a   borosilicate   of 
Al,  Fe,  etc.     R.  U.  prism,  and  stri- 
ated vertically;  hex.  or  triangular 
section.    Test  for  boron.    1,  p.  31. 
Ilvaite.     Orthosilicate  of  Ca  and  Fe. 
Allanite.     Orthosilicate   of   Ca,    Fe, 
Al,  and  the  rare  earths  Ce,  La,  and 
Di.     Test  for  earths,  p.  55. 
Riebeckite,   a  soda-iron  amphibole. 
Civ.    perf.,    prism.    (Z    of    124°). 
Strong  yellow  flame.  See  also  other 
iron  rich  amphiboles,  p.  127. 

Continued  on  next  page. 


114 


DETERMINATIVE  MINERALOGY 


I — A.     Section  g. — Continued. 


Imparts  to  the  Na2CO3 
bead  in  O.F.  a  bluish- 
green  color  (manganese). 
Wolframite  often  decrepi- 
tates violently  B.B. 


Reacts  for  Tungsten,  2,  p. 
71. 


Diff.  fusible. 


Diff.  fusible.       React  for 
Niobium.     1,  p.  51 


Wolframite,    (Fe,Mn)WO4.     M. 

Civ.  pine.  perf.     Black  to  brown, 

or  reddish-brown   streak.     Sp.    G. 

very  high   (  =  7).   H=5-5.5.     Test 

for  W.,  2,  p.  71. 
Alabandite,  MnS.  Olive-green  streak. 


Ferberite,  FeWO4.     M. 


See  under  Iron  Oxides. 
Subdiv.  C. 


Division  1. 


See  Columbite.     I,  Subdiv.  C. 
Samarskite.     Reacts  for  rare  earths 
and  Uranium.     See  pp.  59,  71. 


Ilmenite  (see  beyond,  1,  c.)  may  fuse  and  show  slight,  or  no  mag- 
netic properties. 


Division  I.     Minerals  yielding  a  black  or  dark  colored  streak. 
SUBDIVISION   C.     The  mineral  is  infusible  in  the  forceps  or  on 
charcoal  B.B.,  and  yields  no  sublimate. 


Metallic.  Color  gray.  Easily  scratched 
by  steel.  More  or  less  malleable. 
Insoluble  in  any  single  acid. 


Black,  very  soft,  readily  marks  paper 


Platinum  and  the  platinum  metals. 
Platinum  may  contain  consider- 
able iron  and  be  somewhat  at- 
tracted by  a  magnet.  Iridos- 
mine  is  rather  brittle. 


GRAPHITE,  Hex.  R.  Civ.  basal, 
perf.  Scales  or  plates.  Streak 
black  or  dark  lead-gray  in  re- 
flected light. 

PYROLUSITE,  MnO2,  and  a  little 
H2O.  Prismatic,  fibrous,  radiate, 
also  earthy.  H  =  2.  Test,  2,  p.  48. 
H2O  in  C.T. 


Continued  on  next  page. 


THE  DETETMINATION  OF  MINERALS 
I — C. — Continued. 


115 


Strongly  attracted  by  magnet  without 
heating  in  R.F. 


MAGNETITE,  Fe,O4.  I.  Crys- 
tals U.  octahedral.  U.  granular. 
H  =5.5-6.5.  Streak  black. 

HEMATITE  (see  below),  often  con- 
tains enough  magnetite  to  render 
it  magnetic.  Its  streak  is  dark 
red. 

Franklinite,  a  var.  of  magnetite,  see 
next  page. 

TITANIC  IRON  (in  part)  FeTiO3 
with  var.  proportions  of  FesC^ 
and  Fe2O3.  H=  5.5-6.5.  Streak 
Black. 

U.  granular.     Titanium  test,  1,  p.  69. 

Magnesioferrite,  MgFe2O4.       \ 

Native  Iron,  Fe  and  often  Ni.  \  Rare. 
Meteoric  mostly. 

Awaruite,  FeNi2. 


The  streak  is  red. 


HEMATITE  (Specularite)  Fe2O3. 
Rhomb.  Parting  ||  to  R.  and  base. 
Crystals  commonly  tabular,  mica- 
ceous; also  granular.  Color  steel- 
gray  to  black;  brilliant  in  luster. 
Streak  dark  red.  H  =  5.5-6.5. 

The  mineral  also  occurs  in  reniform, 
botryoidal  masses,  with  splintery 
or  fibrous  structure.  Also  earthy. 
The  hardness  is  less  than  for  the 
crystals,  and  the  streak  is  a  brighter 
red. 

Turgite,  Fe2O3+ Water.  U.  fibrous 
or  splintery,  botryoidal,  earthy. 
Streak  bright  red.  H2O  in  C.T. 

ILMENITE.  See  below,  may  give  a 
dark  reddish  streak. 


Continued  on  next  page. 


116  DETERMINATIVE  MINERALOGY 

I — C. — Continued. 


The  streak  is  some  shade 
of  brown. 


The    streak   is   black    or 
nearly  so. 


LIMONITE  (Brown  Hematite,  Bog 
Iron  ore) ,  2Fe  2O  3.3H  2O  =b .  In  botry- 
oidal,  reniform  or  stalactitic  forms 
and  then  with  finely  fibrous  struc- 
ture. Also  compact,  earthy  and 
soft.  Color  brown  to  almost  black, 
for  hard  vars.  Yellowish-brown 
when  soft.  Streak  yellowish  to 
ochre-brown.  H  =  5-5.5  or  less. 
Abund.  H2O  in  C.T. 

Goethite,  Fe2O3.H2O.  O.  Civ. 
||  to  010,  perf.  U.  with  radiate, 
prismatic  or  fibrous  structure. 
Yellowish,  reddish  to  blackish- 
brown.  Streak  yellowish  to  ochre- 
brown.  H2O  in  C.T. 

Franklinite,(Fe,Mn,Zn)O.(Fe,Mn)2O3. 
I.    Octahedral.    U.  granular.   Color 
black.     Streak  brown.     H  =  6. 
Tests,  Mn,  1,  p.  47.     Zn,  2,  p.  75. 


Psilomelane  (see  below),  may  be- 
come magnetic  B.B.  Its  streak  is 
nearly  black. 

ILMENITE  (Menaccanite)  FeTiO3 
(often  admixed  with  magnetite  and 
hematite).  Rhomb.  Crystals  U. 
tabular.  Commonly  granular. 
Color  black.  H  =  5-6.  Streak  black 
or  slightly  brown  or  reddish.  Titan- 
ium test,  1,  p.  69. 

CHROMITE,  see  below,  may  be- 
come magnetic  B.B. 


Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
I — C . — Continued . 


117 


React  for  Manganese  in 

Manganite,   Mn2O3.H2O.     O.     Pris- 

the soda  bead  test  1,  p. 

matic,  fibrous,  often  radiate.    Civ. 

o 

47. 

||     to    010.     perf.      Color     black. 

g 

Manganite    and    Haus- 

Streak  brown.    H=4,  H2O  in  C.T. 

03 

mannite     have     brown 

Pyrolusite,      MnO2+  Water.      Pris- 

£ 

streaks.     The  rest  have 

matic,  fibrous,  radiate,  also  earthy. 

I 

black,    or   nearly   black 

Very  soft.     H=2.      Test  2,  p.  48. 

O 

streaks. 

H2O  in  C.T. 

£ 

Columbite    (Mn,Fe)(Nb,Ta),O6.    O. 

| 

Color  iron-black,  grayish  or  brown- 

02 

ish-black.     Streak  black  or  brown- 

1 

ish-black.     H=6.     Heavy.    Sp.  G. 

5  to  7.     Tests,  Nb,  1,  p.  51.     Ta, 

1 

p.  67. 

3 

Tantalite,  (Mn,Fe)Ta2O6.    O.    Prop- 

•E 

erties    similar    to    Columbite,    ex- 

2 

8^^ 

cept  Sp.  G.  =7+,  and  little  or  no 

Nb  is  present. 

1 

Psilomelane,  MnO2.MnO  with  K2O, 

PQ 

BaO,  FeaOg  and  H2O.      Noncryst. 

PQ 

massive,      botryoidal,      stalactitic. 

a 

Color  black  to  steel-gray.     Streak 

1 

black  to  brownish-black.     H  =  5-6. 

Jl 

Ba,  3,  p.  28.     H2O  in  C.T. 

1 

Hausmannite,  Mn2MnO4.     T    Octa- 

.2 

hedral,  also  granular. 

Braunite,  3Mn2O3.MnSiO3.  T.  Octa- 

"i 

hedral.     Also  massive. 

1 

Polianite,  MnO2.  T.  U.  cryst.  Color 

light  steel  to  iron-gray.    H  =  6-6.5. 

M 

'•+3 

1 
1 

In  the  borax  bead  reacts 

CHROMITE,  FeCr2O4  (may  contain 

for  Chromium,  1,  p.  36. 

Mg  and  Al).     I.     Octahedral.     U. 

granular.      Color    black.      Streak, 

brown.     H  =  5  up. 

Continued  on  next  page. 


118  DETERMINATIVE  MINERALOGY 

I — C . — Continued . 


« 


11 


Very  high  Sp.  G.  In  the 
Salt  of  Phosphorus 
bead  reacts  for  Uranium, 
1,  p.  71. 


Reacts  for  Ti  (1,  p.  69)  or 
for  Nb  (1,  p.  51). 


Uraninite  (Pitch  Blende,  Cleveite) 
Ur  .  Pb  .  Ra  .  N  .  He  and  various 
other  elements.  Color,  grayish, 
greenish,  brownish,  velvet-black. 
Streak  variable,  but  dark.  Very 
highSp.  G.  (  =  9).  H  =  5.5.  Tests, 
U.  1  or  2,  p.  71.  Gives  a  slight 
coating  of  lead  oxide  with  soda 
B.B.  on  char. 


Nigrine  var.  of  Rutile,  TiO2,  con- 
taining Iron  oxide. 

Fergusonite,  Nb.Ta  Y  Ce,  etc.  Color, 
black.  Streak,  brown.  Becomes 
yellow  B.B.  Ta,  p.  67.  Rare 
earths,  p.  55.  High  Sp.  G. 


THE  DETERMINATION  OF  MINERALS 


119 


Division  II.  The  streak  or  very  fine  powder  is  white  or  light 
colored.  (Minerals  of  non-metallic  luster.) 

SUBDIVISION  A.  The  minerals  are  soluble  in  water.  They 
have  for  the  most  part  a  salty,  bitter,  or  astringent  taste;  for  the 
most  part  are  very  easily  fusible.  With  a  few  exceptions  the 
minerals  of  this  group  are  of  rare  occurrence  and  are  generally 
found  in  dry  or  desert  localities. 

There  are  also  quite  a  large  number  of  rare  species  which  fall 
here  that  are  not  listed.  For  these  see  Brush  and  Penfield's 
"  Determinative  Mineralogy,"  p.  271. 


Color 

React  for  Sulphuric  acid. 

Chalcanthite,     CuSO4.5H2O.       Tri. 

green  or 

Acid  H2O  in  C.T. 

Melanterite,  FeSO4.7H2O.     M. 

blue. 

Chlorides.      The    HNO3 

HALITE  (Common  salt),  NaCl.    I. 

<j>  ^ 

solution   gives   a   white 

Civ.,  cubical  perf.     Intense  yellow 

<u    ^ 

ppt.  with  AgNO3. 

flame  color. 

£  ^r 

Sylvite,   KC1.        I.        Violet  flame 

^  ^ 

color.     Civ.  cubical  perf. 

e  & 

Carnallite,  MgCl2.KC1.6H2O. 

o3    Cu 

Violet  flame  color. 

'  QJ    Q 

Kainite,  MgSO4.KC1.3H2O. 

'>>  "^ 

Jc 

Carbonates.       Effervesce 

Natron,  Na^COs.lOH.O. 

1 

with  acids.    Intense  yel- 

Trona, Na2CO3.HNaCO3.2H2O. 

«    § 

low  flame  color. 

«    0 

c  ° 

0  -3 

Sulphates.     The  solution, 

Thenardite,  Na2SO4.    Intense  yellow 

3  g 

made    acid    with    HC1 

flame  color. 

11 

gives  a  dense  white  ppt. 

Kalinite,       KA1(SO4)2.12H2O.         I. 

w    g 

with  BaCl2. 

Swells  B.B.  and  gives  a  violet  flame 

S  -1 

color. 

•  s  « 

Epsomite,  MgSO4.7H2O. 

i| 

Mirabilite  (Glauber  salt). 

«*H        JJ 

Na2SO4.10H2O4. 

Alunogen,  A12(SO4)2.18H2O. 

Continued  on  next  page. 


120  DETERMINATIVE  MINERALOGY 

II — A. — Continued. 


After  intense  ignition  B.B.,  they  yield 
an  alkaline  reaction  when  placed  on 
moistened  test  paper,  f,  p.  8. 

Nitrates.  Heated  in  a 
bulb  tube  with  HKSO4 
red  vapors  of  NO2  are 
evolved. 

Soda  Niter,  NaNO3.     Rhomb.     In- 
tense yellow  flame  color. 
Niter,     KNO3.      O.      Violet   flame 
color. 

Borates.  Boracic  acid 
test,  2,  p.  31. 

Sassolite  B(OH)3.     U.  in  scales. 
White.     Very  soft.     H  =  l.     Gives 
a  yellow-green  flame  color. 
Borax,  Na2B4O7.10H2O.    M.    Heated 
on  a  loop  of  plat,  wire,  swells  and 
fuses  to  clear  glass,  yielding  intense 
yellow  flame  color. 

Becomes   black  and   magnetic   B.B. 
H2SO4  test. 


B.B.  in  the  R.F.  gives  a  coating  of 
ZnO  on  charcoal.     Infusible. 


Copiapite,  Fe2(Fe.OH)2(SO4)5.17H2O. 
Acid  H2O  in  C.T.  Color  sulphur- 
yellow. 


Goslarite,  ZnSO4.7H2O.     U.  fibrous. 


Division  II.  SUBDIVISION  B.  Heated  alone  intensely  in  the 
C.T.  or  on  charcoal  (sometimes  by  both  methods),  the  mineral  is 
partially  or  wholly  volatile,  or  yields  a  sublimate  (other  than 
water) . 

Most  of  them  fuse. 

Section  a. 


Section  a.  Readily  and  completely 
volatile  when  pure.  Cinnabar  is 
commonly  impure  and  often  leaves 
a  considerable  residue. 


CINNABAR,  HgS.  R.  Color  and 
streak  vermilion-red.  U.  mass- 
ive granular.  C.T.  test,  1,  p.  48. 


Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — B.     Section  a. — Continued. 


121 


Section   a.     Readily   and   completely 
volatile  when  pure. 


Realgar,  As2S2.  Color  and  streak 
aurora  to  orange-red.  Very  soft. 
Gives  a  dark  red  to  yellow  subli- 
mate on  C.T.  Fades  on  cooling. 

Orpiment,  As«S3.  U.  foliated.  Civ. 
pine.  perf.  Very  soft.  Color  and 
streak  lemon-yellow.  Tests  as  for 
Realgar,  above. 

SULPHUR,  S.  O.  Often  in  fine 
crystals,  also  massive.  Brittle  and 
soft.  Color  U.  pale  yellow.  Burns 
with  blue  flame.  Odor  of  SO2. 

Kermesite,      Sb2S2O.     U.  needlelike, 
tufted.     Color  red.     Sectile. 
H  =  1-1.5.     Turns  black  when  hot. 

Arsenolite.     I.  \ 

Claudetite.M./As2°3-     ^  white. 

Senarmontite.   I. 

Valentinite.      O. 


U.  white. 


A  number  of  other  very  rare  minerals  fall  here,  viz.,  Lorandite,  TIAsSa 
(green  flame);  Sal  Ammoniac,  NH4C1;  Mascagnite  (NH4)2SO4;  Calomel, 
HgCl;  Terlinguaite,  HgaCIO;  Egglestonite,  Hg4Cl2O(Hg  test,  1,  p.  48); 
Cotunnite,  PbCl2.  See  B.  &  P.,  p.  258,  and  Dana. 

II— B.    Section  b. 


0)     > 

£  -a 


3    fl 


ffl.    o 

a  '3 


Become  magnetic  B.B.  hi 
the  R.F.  Soluble  in 
HC1. 


Erythrite  (Cobalt  Bloom). 

Co3(AsO4)2.8H2O.     Red  or  crimson 
color.     U.  fibrous  or  earthy. 

Annabergite  (Nickel  Bloom). 
Ni3(AsO4)2.8H2O.        Color    apple- 
green.     U.  fibrous  or  earthy. 

Scorodite,  FeAsO4.2H2O.    O.    Color 
green  or  brown.     U.  cryst. 

Pharmacosiderite,  Fe(Fe.OH)3 
(AsO4)3.6H2O.       I.       U.  cryst.  in 
cubes.     Color  green,  yellow,  brown, 
red. 


Continued  on  next  page. 


122  DETERMINATIVE  MINERALOGY 

II — B.     Section  b. — Continued. 


"S 

1{ 

11 

^     o3 

0> 

^  & 
1  "1 

>    o 

f1 

•S  fl 

£    o 

0 

1 

Become  magnetic  B.B.  in 
theR.F.  Soluble  in  HC1. 

A  few  very  rare  minerals  fall  here. 
See  B.  &  P.,  p.  267. 

Do  not  become  magnetic 
B.B.  in  R.F. 

Mimetite,     Pb4(PbCl)(AsO4)3.       H. 
U.  in  rounded  crystals.     Color  U. 
yellow  or  orange-brown.  Lead  glob- 
ules   w:    soda.      PbCl2     sublimate 
in  C.T. 
Endlichite  —  like  JN'imetite,  but  con- 
tains Vanadii.1..  (1,  p.  72). 

Olivenite,  Cu2(OH)AsO4.       O.       U. 
prism.      Color    blackish    to    olive- 
green  or  brown. 
Chalcophyllite,     7CuO.  As2O6.  14H2O. 
R.     Color  green.     Cryst.   tabular, 
foliated  drusy.     H=2. 
Conichalcite,  a  hydrous  arsenate  of 
Cu  and  Ca.     Color  yellowish-green 
to  emerald-green.       Reniform  and 
massive. 

Proustite      (Ruby   silver),      3Ag2S. 
As2S3.     H.     Ruby-red  color. 
Silver  glob,  after  roasting. 

A  considerable  number  of  very  rare  species  fall  here.  For  their  identifi- 
cation see  Brush  and  Penfield's  ''  Determinative  Mineralogy,"  pp.  259,  260, 
262,  264,  265. 

II — B.    Sections  c,  d,  e. 


B.B.  yields  a  white,  vola- 
tile coating  of  lead  chlo- 
ride (p.  79). 

Pyromorphite,  see  below 
U.  yields  a  slight  coating 
of  lead  chloride. 


Phosgenite,  (PbCl)2CO3.  T.  U. 
cry st.  Colorless  or  white.  Several 
rare  species  fall  here,  see  B.  &  P., 
p.  261. 


Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — B.     Sections  c,  d,  e. — Continued. 


123 


g'S 

*    bf> 

£5 


"  >, 

£  ^3 
o    vi 


These  minerals  are  all 
soft  and  have  high  speci- 
fic gravities. 


CERUSSITE,PbCO3.  O.  U.  cryst. 
white  and  lustrous.  Brittle.  Yields 
a  globule  of  lead  readily  without 
fluxes.  Effervesces  readily  with  di- 
lute HNO3. 

ANGLESITE,  PbSO4.  O.  Cryst. 
and  massive.  Insol.  in  acids.  S. 
test,  2,  p.  67. 

PYROMORPHITE,  Pb4(PbCl) 

(PO4)3.  H.  U.  cryst.  in  hex. 
prisms.  Color  U.  green  or  brown. 
Fuses  to  cryst.  globule.  PbCl  in 
C.T. 

Vanadinite,  Pb4(PbCl)(VO4)3. 
H.  U.  cryst.  in  hex.  prisms. 
Color  red,  yellow,  brown.  Vana- 
dium test,  1,  p.  72. 

WULFENITE,  PbMO4.  T.  U. 
cryst.  tables  or  plates.  Color 
yellow,  orange,  brownish.  Mo. 
test,  2,  p.  49. 

Crocoite,  PbCrO4.  M.  U.  cryst. 
Color  bright  red.  Cr.  test,  1,  p.  36. 

Descloizite,  a  hydrous  vanadate  of 
lead  and  zinc.  Color  red,  brown 
to  black.  May  react  for  Cu. 


(A  considerable  number  of   rare  species  also  fall  here. 
Penfield,  pp.  259,  260,  261.) 


See  Brush  and 


Section  d.  B.B.  yields  a  coating  of  bismuth  oxide;  confirm 
by  2,  p.  29. 

Bismutite,  BiO(Bi.2OH)CO3  (white,  green,  yellow),  and  a  few 
other  species,  all  very  rare,  fall  here.  See  Brush  and  Penfield,  p.  262. 


Section  e.  Several  very  rare  species  containing  antimony  and 
yielding  an  antimony  oxide  sublimate  on  char.  faU  here.  See 
Brush  and  Penfield,  p.  263. 


124  DETERMINATIVE  MINERALOGY 

II— B.     Sections  f,  g,  h. 


Section  /.  The  following  zinc  min- 
erals while  infusible  or  fusible  with 
difficulty,  yield  on  strong  heating 
B.B.  in  the  R.F.  a  yellowish  coat- 
ing of  ZnO  on  charcoal  1,  p.  74. 
Calamine  and  Willemite  fused  with 
soda  and  char,  give  the  ZnO  coating 
more  satisfactorily  than  when 
heated  alone. 


Section  g.     Yield     a     sublimate     of 
Molybdenum  oxide,  1,  p.  49. 


Section  h.  Easily  fusible — partially 
volatile  and  leave  a  globule  of  silver 
B.B.  on  char.  Cut  like  wax  with 
a  knife  (Sectile).  For  tests  for  Cl, 
I.  and  Br.  see  1,  p.  35,  and  pp.  31, 
42. 


SPHALERITE  (Blend),  ZnS.  I. 
Civ.  in  six  directions  duodeca- 
hedral  perf.  U.  cryst.  granular. 
Color  yellow,  red  to  brown.  Streak 
yellow  to  light  brown.  Gives  H2S 
w.  effervescence  in  HC1. 

SMITHSONITE,  ZnCO3.  R.  U. 
botryoidal.  CO2  in  acids.  Vari- 
ous colors. 

CALAMINE,  (ZnOH)2SiO3.  O. 
Cryst.,  prism.,  radiated,  encrusted, 
or  botryoidal  in  structure.  Yields 
gelatinous  silica  with  acids.  H2O 
inC.T. 

Willemite,  Zn2SiO4.  R.  U.  granular 
or  mass,  cryst.  Color  green,  yel- 
lowish green,  or  brown.  Yields 
gelatinous  silica  with  acids,  U. 
occurs  with  franklinite. 

Zincite,  (Zn,Mn)O.  Color  U.  dark 
red.  Streak  yellow. 


Molybdic  Ochre,  Fe2O3.3MoO3.7H2O. 
Yellow.  Massive. 

Molybdite,  MoO3.  In  fibrous,  tufted 
also  powdery  incrustations,  also 
massive.  Color  yellow.  Very  soft. 


Cerargyrite,  AgCl.  I.  Cubical  crys- 
tals; also  wax-like  masses.  Color 
brown,  gray  to  greenish. 

Bromyrite,  AgBr.     I. 

lodyrite,  Agl.  I.  Isom.  mixtures  of 
AgCl,  AgBr,  and  Agl  occur.  See 
species  Embolite,  Idobromite.  The 
color  of  these  varies  from  yellow  to 
yellow-green. 


THE  DETERMINATION  OF  MINERALS 


125 


Division  II.  SUBDIVISION  C.  The  mineral  fuses  B.B.  but  is 
non-volatile  and  yields  no  sublimate  either  in  the  C.T.  (except 
sometimes  water)  or  on  charcoal. 

Section  a.  On  fusion  in  the  R.F.  the  mineral  blackens,  or  re- 
mains black,  and  when  cold  is  attracted  by  a  magnet  (iron). 


Difficultly  fusible.  Effervesce  in 
warm  dilute  HC1  or  HNO3.  U. 
cryst.  and  show  a  cleav.  in  three 
directions.  (Rhomb.) 


Micaceous.  Civ.  perf.  basal.  Yields 
thin  leaves  or  flakes.  Black  or 
greenish  black  in  color. 


Elongate  or  bladed  crystals,  often 
with  radiate  grouping.  Color 
bronze  or  yellow. 


Soluble   in   HC1   yielding  gelatinous 
silica  upon  evaporation  (1,  p.  57). 


SIDERITE,  FeCO3.  R.  Color  light 
brown,  becomes  dark  brown  on 
alteration.  H=  3.5-4. 

Ankerite  (Ca)(Mg,Fe)(CO3)2.  R. 
Color  gray,  light  brown. 

RHODOCHROSITE,  (Mn,Fe)CO3. 
R.  Color  U.  pink  or  red,  rarely 
brown.  H  =  3.5-4.5.  Mn,  test  1, 
p.  47. 


Lepidomelane  (Iron  mica).  Com- 
plex silicate  of  Fe  and  Al.  Yields 
gelatinous  silica  with  acids. 


Astrophyllite.  O.  Civ.  pine.  perf. 
Complex  silicate  containing  Na,  K, 
Fe,  and  Ti.  Decomposed  with 
separation  of  SiC>2  by  acids. 


ANDRADITE  (Garnet  in  part), 
Ca3Fe2(SiO4)3.I.  U.  cryst.  dode- 
cahedral,  also  granular.  U.  brown 
or  greenish-brown.  Gelatinizes 
imperfectly. 

Allanite,  complex  silicate  containing 
Fe,  Al,  Ca  and  the  Rare  Earths. 
Color  brown  to  pitch-black.  Test 
for  earths,  p.  55.  Swells  and  froths 
during  fusion. 


Continued  on  next  page. 


126  DETERMINATIVE  MINERALOGY 

II — C.     Section  o.^-Continued. 


Soluble   in   HC1  yielding  gelatinous 
silica  upon  evaporation  (1,  p.  57). 


Ilvaite,  silicate  of  Ca  and  Fe.     Color 

black. 

Fayilit",  Fe,SiO4.  O.  Color  yel- 
lowish to  dark  yellowish-green. 
Luster  resinous. 

Stilpnomelane,  a  complex  hydrous 
silicate  of  iron,  magnesium  and 
aluminum.  Minute  plates,  fibrous, 
radiated.  Color  green  to  black, 
bronzy. 

Essentially  hydrous  sili- 
cates of  iron  and  alumi- 
Thuringite      nium.     Compact  aggre- 
Chamosite   1  gation  of  minute  scales 
or  o elites.     Color  olive- 
green  to  almost  black. 
For  other  species  see  B.  &  P.,  p.  269. 


Phosphates,  test  2,  p.  52. 

(A  considerable  number  of 
other  rare  phosphates 
fall  here.  See  Brush- 
Penfield,  p.  268.) 


Vivianite,  Fe3(PO4)2.8H2O.  M.  U. 
prism.  Civ.  pine.  perf.  Color 
blue,  bluish  green,  colorless. 

Triphylite,  Li(Fe,Mn)PO4.  U.  mass. 
Color  light  blue,  green,  or  gray. 
Crimson  flame  (Li). 

Triplite,  contains  Fe,  Mn,  and  F. 
U.  mass.  Color  chestnut  to  black- 
ish brown. 

Childrenite,  contains  Fe,  Mn,  Al. 
O.  U.  cryst.  Color  yellowish- 
brown  to  brownish -black. 


Sulphates,  test  1,  p.  66. 
In  the  C.T.  give  acid 
water.  (Some  only  on 
intense  ignition.) 


Jarosite,     K(Fe.2OH)3(SO4)2.         H. 

U.    cryst.      Color    ochre-yellow    to 

clove-brown. 
(A  large  number  of    rare   sulphates 

fall  here.     See  Brush-Penfield,  pp. 

266-7. 


Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 


127 


II — C.     Section  a. — Continued. 


Tungstate,  2,  p.  69.   Very 
high  Sp.  G. 


B.B.  fuses  with  marked 
intumescence.  Arfed- 
sonite,  Riebeckite,  and 
crocidolite  contain  much 
Na  and  Fe  and  give  a 
strong  yellow  flame 
color. 


Fuse    quietly    B.B.    with 
little  or  no  intumesence. 


(See  also  certain  black 
varieties  of  Augite  and 
Hornblende  which  may 
contain  sufficient  Fe  to 
render  them  magnetic 
B.B.  (Div.  II,  D-c.) 
See  also  difficultly  fusi- 
ble iron  oxides.  Div. 
I-C.) 


WOLFRAMITE,  (Fe,Mn)WO4.  M. 
Civ.  pine.  perf.  Streak  and  color 
dark  reddish-brown  to  black. 


Color  black.  U. 


EPIDOTE,  Ca2Al(OH)(AlFe)2 
(SiO4)a.     M.     Color  U.  yellowish- 
green.     U.  cryst.  prism.     Civ.  basal 
perf.     Ceases  to  intumesce  after  a 
little  heating. 

Arfvedsonite, 

Riebeckite, 

cryst.    prism.      Civ.    prism, 
perf. 

Crocidolite,  color  bluish, 
fibrous.  See  also  other 
vars.  of  hornblende. 

TOURMALINE,  see  below. 


II 


TOURMALINE,  A  borosilicate  of 
Al,Fe,  etc.  R.  U.  prism,  and 
striated  vertically;  hex.  or  tri- 
angular section.  Color  black. 
Boron  test  1,  p.  31. 

ALMANDITE  (garnet  in  part), 
Fe3Al2(SiO4)3.  I.  U.  cryst.  in 
duodecahedrons  or  trapezohedrons; 
also  granular.  Color  dark  red. 

EPIDOTE,  see  above. 

Aegerite, 

Acmite, 

U.  in  prism,  crystals.  Color  U. 
green  to  dark  green,  rarely  brown- 
ish. Yellow  flame  color. 


NaFeSi2O6.     M. 


Continued  on  next  page. 


128  DETERMINATIVE  MINERALOGY 

II — C.     Section  a. — Continued. 


or  nearly  so  in  hy- 
c  or  nitric  acid.  The 
of  this  group  are  for 
part  silicates.  Test 

Glauconite,  a  hydrous  silicate  of  iron 
and  potassium.  Loosely  granular 
earthy,  massive.  Color,  varying 
shades  of  green.  K.  test  1,  p.  53. 
Some  vars.  are  slightly  soluble. 

!:1 

Prismatic,  fibrous,  lamel- 
lar. 

Anthophyllite,  (Mg,Fe)Si2O6. 
Gray,  green,  brownish. 

Division  II.  SUBDIVISION  C.  Section  b.  After  fusion  B.B. 
the  fragment  yields  an  alkaline  reaction  on  moistened  turmeric  or 
reddened  litmus  paper.  See  f,  p.  8. 


Yellowish-red    flame  color;    not  dis- 
tinctive.    (Use  Spectroscope). 


Strong  yellow  flame  color. 
H  =  2.5. 


GYPSUM  (Selenite),  CaSO4.2H2O. 
M.  Cryst.  fibrous,  granular,  mass. 
(Alabaster  in  part).  Civ.  pine, 
perf .  Crystals  may  be  split  easily 
into  thin  plates.  U.  white  or  pink- 
ish. Crystals  colorless.  Sp.  G. 
=  2.32.  Very  soft.  H  =  2.  Sol- 
uble in  dilute,  hot  HC1.  Test  3, 
p.  33. 


ANHYDRITE,  CaSO4.  O.  U.  mass. 
When  cryst.  Civ.  in  3  directions 
at  nearly  rt.  angles.  U.  white. 
Sol.  in  hot  dilute  HC1.  H  =  3-3.5. 


Cryolite,  Na3AlF6.  M.  Poor 
pseudo-cubic  civ.  F.  test  1,  p.  39. 

Gay-Lussite,  Na2CO3.CaCO3.5H2O. 
M.  U.  cryst.  Intense  yellow 
flame  color.  Effervesces  freely  in 
dilute  acids.  H2O  in  C.T. 


Continued  on  next  page. 


THE  DETERMINATION  OP  MINERALS 
II — C.     Section  b. — Continued. 


129 


Strong  yellowish-red  flame  color. 
Fragments  U.  decrepitate  B.B. 
(Use  Spectroscope.) 


Bright  red  or  crimson  flame  color. 
(Use  Spectroscope.) 


Yellow-green  flame  color.     High  spe- 
cific gravity.     (Use  Spectroscope.) 


FLUORITE  (fluorspar),  CaF2.  I. 
U.  cryst.  in  cubes.  Civ.  octahedral 
(4  directions)  perf.  Color  yellow, 
green,  purple,  also  colorless.  H  =  4. 
Sp.  G.  3.18.  F.  test,  1,  p.  39. 


Celestite,  SrSO4.  O.  U.  cryst.  Civ. 
basal  perf.  and  prism.  Colorless 
or  white.  H=3.5  Sp.  G.=3.9. 
Diff.  sol.  Sr  test,  3,  p.  64. 


BARITE,    BaSO4.      O.      Cryst.    U. 

tabular;    granular,  also  compact. 

Civ.    basal    perf.    and    prism.    U. 

white.     H  =3.3-5.     Sp.    G.=4.5. 

Nearly    insol.    in    hot    HC1.     Ba 

test,  3,  p.  28. 
Witherite,  BaCO3.    O.    (Pseudo-hex.) 

U.  cryst.  mass.    U.  white.    H  =  3.5. 

Sp.    G.  =3.9.     Effervesces    readily 

with  dilute  HNO3. 


For  other  species,  see  Brush  and  Penfield,  p.  274. 

Division  II.  SUBDIVISION  D.  The  mineral  fuses  in  the 
forceps  B.B.  but  does  not  become  magnetic,  volatilize,  yield  a 
coating  on  charcoal,  nor  give  an  alkaline  reaction. 

Section  a.  The  mineral  fuses  to  a  colorless  glass.  A  number 
of  species  fuse  to  a  clear  glass  which  superficially  appears  white, 
owing  to  the  presence  of  bubbles.  For  such  see  also  under 
Section  b,  beyond. 


Special  reaction 

Yields  a  red  flame  colora- 
tion. 

Lepidolite,  see  beyond. 
Spodumene,  see  beyond. 

Yields  a  yellowish-green 
flame  coloration. 

Datolite,  see  beyond. 
Danburite,  see  beyond. 

Continued  on  next  page. 


130  DETERMINATIVE  MINERALOGY 

II — D.     Section  a. — Continued. 


I.I 


Fuse  with  swelling,  branch- 
ing or  intumescence. 


Lepidolite 
Spodumene 
Datolite 
Stilbite 


See  below. 


Yields  a  green  flame  color. 


Datolite,  Ca(B.OH)SiO4.  M.  U. 
in  white  or  colorless  crystals  of 
complex  habit.  H  =  5  to  5.5. 
Fus.  (  =  2)  with  marked  intumes- 
cence. H2O  in  C.T. 

Danburite,  CaB2Si2O8.  O.  U.  cryst. 
prism.  H  =  7.  Rather  insoluble. 


Yields  yellow  flame  color. 


w  ^ 


NEPHELITE,  NaAlSiO4.  U.  crys- 
talline, mass.  H  =  5.5-6.  Greasy 
luster.  Colorless,  gray,  white,  pink. 
Whitened,  altered  portions  yield 
H2O  in  C.T.  (Kaolin).  U.  assoc. 
with  feldspar. 
ANALCITE.  NaAl(SiO3)2.H2O.  I. 

U.  cryst.  in  trapezohedrons.     U. 

colorless  or  white.     Yields  rather 

poor  jelly. 

NATROLITE,  Na2Al2Si3Oi0.2H2O. 
O.  U.  cryst.  in  slender  prisms  or 
needles.  White. 

Sodalite,     Na4(AlCl)Al2(SiO4)3.     U. 
mass.     Color  deep  blue.     Cl.  test. 


Decomposed  with  the  separation  of 
non-gelatinous,  powdery  silica  (see 
2,  p.  58). 


LABRADORITE,  NaAlSi3O8.CaAl2 
Si2Os.  Tri.  Civ.  perf.  in  two  direc- 
tions at  right  angles.  One  civ.  face 
U.  striated.  Partially  decomposed 
by  acids. 


Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — D.     Section  a. — Continued. 


131 


Decomposed  with  the  separation  of 
non-gelatinous,  powdery  silica  (see 
2,  p.  58. 


ANALCITE,    see    above.     U.    gives 

a  poor  jelly. 
Stilbite,  H4(Ca,Na2)Al2(SiO3)6.  4H2O. 

U.     cryst.    in     sheaf-like     groups. 

Fuses   with    swelling    and  intumes- 

sence.     H2O  in  C.T. 


Soluble  in  HC1  but  without  separation 

Ulexite,     NaCaB6O9.8H2O.       White, 

of  silica  or  gelatinization. 

silky  fibers.     Boron  test,  2,  p.  31. 

B.B.   gives  a  red  flame 

Spodumene,      LiAlSi2O6.     M.     U. 

coloration    (the    red    is 

cryst.  as  flat  prisms  often  of  large 

sometimes     partly     ob- 

size.    Tough,  splintery  prism,  civ. 

scured  by  sodium). 

H  =  6.5-7.     B.B.     U.    throws    out 

branches. 

CD 

Lepidolite  (Lithia  mica),  silicate  of 

g 

Li   and  Al.     Micaceous  in  habit. 

K 

Civ.    basal   perf.,    yielding    plates 

i 

or    flakes.     Colorless,    pink,    lilac. 

6 

Fuses    with    much    intumescence. 

w 

H=2. 

i 

Green  flame. 

Danburite,  see  above. 

8 

Possesses  two  good  cleav- 

ALBITE,    NaAlSi3O8.     Tri.  Cryst. 

9 

ages     at     nearly     right 

and  U.   of  tabular  habit.     H=6. 

o 

angles    to    each    other. 

Contains  no  Ca  and  but  little  or 

3 

One  cleavage  face  com- 

no K.     (Test,  6,  p.  54.) 

"g 

monly   shows   fine   par- 

OLIGOCLASE, 3NaAlSi3O8. 

• 
q 

HH 

allel  striations. 

CaAl2Si2O6.     Tri.     Reacts    for    a 

little  Ca  but  little  or  no  K. 

Prismatic  habit.       Good 

TREMOLITE,  CaMg3(SiO3)4.     M. 

cleavage     at    angle    of 

Color  white  or  gray.     H  =  5  to  6. 

about  125°. 

Test  4,  p.  58. 

Continued  on  next  page. 


132 


DETERMINATIVE  MINERALOGY 


II — D.     Section  a. — Continued. 


1 

.g 

s 

£ 

§  . 

si 
Is 

J2  ^ 
1  a 

IH 

Finely  fibrous  habit. 

Tremolite   Asbestos.    See  Tremolite 
above.     White  color. 

Monoclinic     crystals. 
Prism  angle  about  87°; 
also  granular. 

DIOPSIDE,     CaMg(SiO3)2.          M. 
Color,    white,    gray,    light    green. 
H  =  5-6.     Test  4,  p.  58. 

Color  bluish.  Prismatic 
to  almost  fibrous  struct. 

Gkucophane,  Na2Al2Si4O.2+(Mg,Fe)4 
Si4Oi2.     M.     Yellow  flame  color. 

Compact  structure. 
Color  white,  gray,  green- 
ish. 

Jadeite,   NaAlSi2Oe   (Jade  in  part). 
Yellow  flame  color. 

II — D.  Section  b.  The  mineral  fuses  in  the  forceps  B.B.  to 
a  white,  glass,  enamel,  or  slag. 

See  general  remarks,  p.  94,  and  note  that  slight  impurities 
or  variations  in  composition  may  cause  the  mineral  to  fuse  white 
or  colored,  whereas,  if  pure  it  would  fall  in  Section  a,  and  it  is  well 
to  compare  the  minerals  there  listed  where  any  uncertainty  exists. 


Special  reactions  or  structures. 

Yields  a  red  flame  colora- 
tion. 

Lepidolite,  see  Section  a. 
Spodumene,  see  Section  a. 
Amblygonite,  see  below. 
Petalite,  see  below. 

Yields  a  greenish  flame 
coloration. 

Boracite,  see  below. 
Colemanite,  see  below. 

Fuse  with,  swelling, 
branching,  or  intumes- 
cence. 

Scolecite,               Chabazite, 
Mesolite,               Stilbite, 
Thomsonite,         Heulandite, 
Laumontite,          Apophyllite, 
Spodumene,          Lepidolite, 
Cancrinite. 
For  these,  see  below. 

Distinct  micaceous  struc- 
ture. 

Lepidolite   1 
Muscovite  \  See  beyond. 
Margarite   J 

Continued  on  next  page. 


THb  DtiTEtt'M  NATION  UP  MlWE'ftALS 
II — D.     Section  6. — Continued. 


133 


Dissolves  with  effervescence  in  dilute 
HC1  or  NHOs   (warming  may  be 
necessary). 

Cancrinite,  H6(Na2,Ca)4(Al.NaCO3)2 
Alfi(SiO4)9.      U.    mass.      Color    U. 
yellow.     Swells    and    froths  during 
fusion.     Yields     gelatinous     silica. 
H  =  5.5-6. 

Decomposed  by  HC1  with  the  separa- 
tion   of    a    bright    yellow    residue, 
Tungstic  acid.     Test  1,  p.  70. 

Scheelite,  CaWO4.     T.     Color  white 
High  Sp.  G.=6.     H  =4.5-5. 

II 

o>    || 

°£ 

!l 

Ja    ° 

|| 

.jU 

"S   ^ 

•§  g 

So  ^ 

If 

£3 

11 

*  £ 
a  0 

§5 
§< 

u  ^ 
a  ^ 

1- 
?  c£ 

d 

il 

§£H 
Q 

Q 

Color  usually  blue. 

Lazurite.     Complex  silicate  of  Na, 
Ca,  and  Al  containing  S.    U.  mass. 
Gives  off  H2S  with  HC1.     Yellow 
flame. 
Helvite,  similar  to  Lazurite. 
Haiiynite.     Composition    similar    to 
lazurite.     Contains  S  as  SO4;   does 
not  give  H2S  but  HC1  sol.  gives 
ppt.  with  BaCl2. 
Noselite,  similar  to  Haiiynite. 

U.  in  compact  acicular, 
radiate  aggregates. 

Pectolite,    HNaCa2(SiO3)3.      H  =  5, 
two  perf.  civs. 

Possesses  two  good  cleav- 
ages at  nearly  right 
angles  to  each  other. 

Anorthite,  CaAl2Si2O8.    Tri.    H=5. 

Contain  Al,  and  Ca  (tests 
4,  p.  58).  U.  prism,  in 
habit,  often  in  more  or 
less  compact  clusters 
with  radiating  arrange- 
ment, except  Gehlenite, 
which  U.  forms  short, 
square  crystals. 

Scolecite,          CaAl(A1.2OH)(SiO3)8. 
2H2O.      Fuses    to    a    voluminous 
frothy  slag. 
Mesolite,       "i  Complex   silicates   of 
Thomsonite,  \       Na,  Ca,  and  Al. 
Laumontite,  J  H2O  in  C.T. 
Gehlenite,  Silicate  of  Ca,Mg,Fe  and 
Al.     No  H2O  in  C.T.     Fuses  with 
diff.  to  a  gray  slag. 

Continued  on  next  page. 


134  DETERMINATIVE  MINERALOGY 

II — D.     Section  b. — Continued. 


White    or    colorless.     T. 

Apophylite,    see    beyond.     Gives    a 

crystals. 

poor  jelly. 

Greasy  luster. 

Nephelite,  see  Section  a. 

t 

Fuse      with    swelling,    or 

WERNERITE,  complex  silicate  of 

1 

intumescence,    or 

both. 

Na,  Ca  and  Al.    T.    U.  cryst.    In- 

& 

Prehnite  and  Wernerite 

tense  yellow  flame.     H  =  5-6. 

•3 

are    harder   than 

glass; 

Prehnite,    H2Ca2Al2(SiO4)3.      U.    in 

CO 

the    others    are    softer. 

form  of  greenish  botryoidal  cryst. 

I 

All  but  Wernerite 

yield 

crusts.       H  =  6-6.5.      Decomposes 

E 

H2O  in  C.T. 

slowly  with  HC1. 

1 

Chabazite.       R.       U.     in 

0 

rhomb,  crystals                       _,.      ^ 

^ 

Stilbite.     M.     U.  cryst.  in     Q  ?  g4 

43 

sheaf-like  bundles.     Civ.      ^  §  1 

'S 

pine.  perf.     Pearly  luster          ^  ££. 

parallel  civ.  face.                     W  P  g 

Heulandite.    M.    U.  cryst.      JL  K*  g 

W  06 

in    lozenge-shaped    crys-     J^  2L  ',  o 

s  ^ 

tals.       Civ.     pine.     perf.      91  ^  "* 

A 

O  of 

Pearly  luster  parallel  to          ^  p 

w  **• 

civ.  face. 

«    o 

Other  rare  species, 

some 

Apophyllite,  H7KCa4(SiO3)8  .4iH2O. 

r§  <S 

containing    Ba   and  Sr, 

T.       U.     cryst.    Civ.    basal    perf. 

>>  2 

(zeolites)  fall  here. 

See 

Pearly   luster  parallel   base.     H  = 

|| 

Brush-Penfield,  p. 

282. 

4.5-5.     Test  for  K.     6,  p.  54. 

o  ^ 

SH     bfi 

Fuses    without    intumes- 

WOLLASTONITE,    CaSiO3.       O. 

II 

cence. 

Civ.  pine.  perf.     U.  Columnar  ag- 

gregates.    Color.  U.  white  or  gray. 

fi 

May  give  a  poor  jelly.     H  =  5. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — D.     Section  b. — Continued. 


135 


Soluble  in  hydrochloric  or  nitric  acids, 
but  do  not  belong  to  foregoing  sec- 
tions. 


Boracite,  Mg7Cl2B16O3o.  I.  U.  cryst.; 
cubes,  tetrahedrons.  Cl  test  1,  p.  35. 
Greenish  flame.  H  =  7. 

Colemanite,  Ca2BeOu.5H2O.  M.  Civ. 
010,  perf.  Cryst.;  also  granular, 
compact.  Colorless,  white 

H  =  4-4.5.  Yellowish-green  flame. 
Decrepitates,  exfoliates  and  fuses 
imperfectly.  Ca  test  3,  p.  33. 


Amblygonite,  Li(AlF)PO4.  Tri.  U. 
cryst.  mass.  Red  flame.  H  =  6. 
Phosphorus  test,  2,  p.  52> 


Beryllonite,  NaBePO4.  O.  Color- 
less. Cryst.  Strong  yellow  flame, 
tinged  with  green. 


Insoluble  in  acids. 

"3 

1 

•8 

43 

1 

1 

43 

% 

J2 

1 
1 

1 

Fuses  easily  with  intu- 
mescence and  yields  a 
crimson  flame  (rarely 
obscured  by  sodium). 

Le  pi  do  lite,  see  Section  a,  p.  131. 

Micaceous  structure.  Can 
be  split  into  thin  leaves, 
plates  or  scales.  Fuses 
rather  difficultly. 

MUSCOVITE,  H2KAl3(SiO4)3.     M. 
Hex.  or  rhombic  plates.    Civ.  basal 
perf.        Civ.   plates   colorless  and 
elastic.      Found   U.    with   feldspar 
and  quartz.     H=2. 
Margarite,        H2CaAl4Si2O,2.         M. 
Color  U.   pink.     Civ.   basal  perf. 
Leaves  brittle. 
See  also  Paragonite,  soda-mica,p.  145. 

Phosphate  test,  2,  p.  52. 
Be  test,  p.  28. 

Herderite,  Ca[Be(F,OH)]p64.  M.  U. 
cryst.  Colorless.  H  =  5. 

Finely  fibrous. 

Asbestos,  see  Tremolite,  Section  a, 
p.  131. 

Continued  on  next  page. 


136  DETERMINATIVE  MINERALOGY 

II — D.     Section  b. — Continued. 


Insoluble  in  acids. 

Hardness  greater  than  steel. 

Colors  the  flame  crimson 
(Lithia). 

Spodumene.     Sec  Section  a  above. 
Petalite  (Li,Na)Al(Si2O5)2.     M.     U. 
mass.     Civ.     basal     perf.     Fuses 
quietly. 

Fuses  with  intumescence. 

ZOISITE,  Ca2(Al.OH)Al2(SiO4)3. 
M.  U.  cryst.  prismatic  or  colum- 
nar. U.  striated.  Civ.  pine.  perf. 
Color  white,  gray  and  various  light 
shades.  H  =  6. 

TOURMALINE,  a  boro-silicate  of 
Al.  and  other  elements.  R.  U. 
prism,  and  striated  vertically;  hex. 
or  triangular  section.  Color  green, 
pink,  white.  H  =  7-7.5.  Boron 
test,  1,  p.  31. 

Possess  two  perfect  cleav- 
ages at  right  angles 
(parallel  to  the  base  and 
the  clino,  or  bracy- 
pinacoid) 

ORTHOCLASE,    KAlSi3O8.         M. 
(Microcline,  Trie.)    Often  in  typical 
monoclinic  crystals.     Civ.  surfaces 
unstriated.      White,    pink,    green. 
H=6.    Sp.  G.=2.57,  F  =  5.  Potash 
test,  6,  p.  53. 
ALBITE,    NaAlSi3O8.     Trie.    Habit 
is   commonly  tabular.      U.  white. 
Gives  little  or  no  K  test.     H  =  6. 
Sp.  G.=2.62.     F=4-4.5. 

OLIGOCLASE,  3NaAlSi3O8  .CaAl2 
Si2O8.  Trie.  The  basal  cleavage 
surface  U.  shows  fine  parallel 
striae.  U.  white.  H  =  6.  Sp.  G. 
=2.66.  F  =  4-4.5.  Reacts  for 
lime.  (4,  p.  58.) 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — D.     Section  b. — Continued. 


137 


Insoluble  in  acids. 

Hardness  greater  than  steel. 

Two  cleavages  at  angles 
of  55  and  125°. 

TREMOLITE,  CaMg3Si3O12.  M.  U. 
prism,  in  habit.  Color  U.  white 
or  gray.  H  =  5-6.  Ca  and  Mg 
test  4,  p.  58. 

Crystals  are  prismatic  and 
have  a  nearly  square 
cross-section. 

PYROXENE    (var.    Diopside),    Ca 
MgSi2O6.      M.     Prism,  civ.  poor. 
Often  shows  a  basal  parting.    Color 
white,   pale  green.     H  =  5-6.     Ca 
and  Mg  tests,  4,  p.  58. 

U.  in  simple  Hex.  prisms 
of  yellowish  or  greenish 
color;  Diff.  fusible. 

Beryl,  Be3Al2(SiO3)6.  H.  H  =  7-7.5. 
U.  occurs  with  quartz  and  feldspar. 
Be  test,  p.  28. 

U.  in  dodecahedral  or 
trapezohedral  crystals. 

Grossularite    (Garnet  in  part), 
Ca3Al2(SiO4)3.    I.    Often  granular. 
Color  white,  pink,  pale  yellow  or 
green.       Gelatinizes    after    fusion. 
H  =  7. 

Strong  yellow  flame  color. 

Jadeite,  NaAlSi2O6.  U.  massive. 
White,  pale  green.  H  =  6.5-7. 

Division  II.  SUBDIVISION  D.  Section  c.  The  mineral  fsues 
in  the  forceps  to  a  colored  or  black  glass,  enamel  or  slag. 

Impurities  or  variations  in  composition  may  cause  some 
minerals  listed  in  Sections  a  or  6  to  fall  here.  The  minerals 
should  therefore  be  compared  with  those  in  corresponding  sections 
of  a  and  b  if  any  uncertainty  exists. 


Show  special 
reactions. 

Yield  a  green  flame  colora- 
tion.    Strongly  colored, 
red  or  green. 

See  Copper  Minerals,  beyond. 

Continued  on  next  page. 


138  DETERMINATIVE  MINERALOGY 

II — D.     Section  c. — Continued. 


Show  special  reactions,  colors  or  structures. 

Yields  a  red  flame  colora- 
tion. 

See  Lithium  Minerals,  beyond,  p.  142. 

Fibrous,  silky  structure. 

Chrysotile,  Asbestos,  see  beyond. 

Dodecahedrous,  trapezo- 
hedrous. 

Garnets,  see  beyond,  p.  142. 

Bright  yellow  color. 

Carnotite,  see  beyond,  p.  142. 

Possess  amicaceous  struc- 
ture. When  fine  grained 
they  consist  of  an  ag- 
gregate of  small  sepa- 
rable scales  or  plates. 
Larger  crystals  can  be 
split  easily  into  thin 
plates,  owing  to  the 
highly  perfect  basal 
cleavage.  The  crystals 
are  all  monoclinic,  but 
are  pseudo-hexagonal  or 
orthorhombic  in  aspect 
and  U.  of  tabular  habit. 
H=  2.5-3.  All,  except 
vermiculites,  are  only 
slightly  affected  by 
nitric  or  hydrochloric 
acid. 

MUSCOVITE,  H2KAl3(SiO4)3.  See 
Section  b,  above. 

BIOTITE,  (H,K)2(Mg,Fe)2(Al,Fe)2 
(SiO4)3.  M.  Often  in  tabular 
crysts.  Thin  leaves,  U.  brown  or 
greenish-brown,  flexible  and  elastic. 
Gives  little  water  when  heated  in- 
tensely in  C.T. 

PHLOGOPITE.  Like  biotite,  but 
contains  more  Mg,  also  Fluorine. 
(3,  p.  40,  may  give  acid  H2O  in  C.T. 
Thin  leaves,  U.  brown  or  reddish- 
brown,  flexible  and  elastic. 

Roscoelite,  a  vanadium  mica.  Clove 
to  dark  greenish-brown.  (V.  test, 
1,  P.  72.) 

CHLORITE  GROUP.     M.     Often 

in  tabular  crysts.  Hydrous  sili- 
cates of  Mg,  Fe,  and  Al.  (Vars. 
clinochlore,  ripidolite,  penninite, 
etc.)  Color  dark  green.  Thin  leaves, 
are  flexible  but  not  elastic.  Abun- 
dant H2O  in  C.T. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — D.     Section  c. — Continued. 


139 


Show  special  structures. 

Foliated,  micaceous  (see 
preceding  page). 

/ 

TALC,  H2Mg3(SiO3)4.    M.    U.    Foli- 
ated.   White,  gray,  greenish.    Very- 
soft,  soapy.    (H  =  l).    Diff.  fusible. 
Vermiculites,   complex  hydrous  sili- 
cates,  of   Mg  and  Al.     Exfoliate 
prodigiously     B.B.       Decomposed 
by  acids. 

Chlorotoid,  see  II  —  E.  Section  g, 
beyond. 

Show  special  reactions.  Fuses  with  intumescence,  swelling  or  cracking 
apart. 

Soluble  in  dilute  HNO3 
or  HC1  and  yield  gela- 
tinous silica  upon  evap- 
oration. (1,  p.  57.) 

Allanite,     cerium     bearing    Epidote 
(see    below).      M.      Rare    earths, 
p.  55.     Color  brown  to  pitch-black 
H  =  5.5-6. 
Gadolinite,     FeBe2Y2Si2Oio.     Green- 
ish to  brownish-black.     Swells  and 
cracks  B.B.    Be  test,  p.  28.    Y.  test, 
p.  55. 

Decomposed  by  HC1, 
yielding  non-gelatinous 
silica  (2,  p.  58). 

Prehnite,  see  Section  b. 

Insoluble  or  nearly  so  in 
HC1  or  HN03. 

EPIDOTE,  Ca2(Al.OH)(Al,Fe)2 
(SiO4)3.  M.  U.  in  prismatic  or 
columnar  crystals.  Civ.  basal  perf. 
(||  to  elongation).  Color  yellow- 
green.  H  =  6-7.  Intumesces  only 
at  first.  Gelatinizes  after  fusion. 

VESUVIANITE,  essentially  a  Ca.Al 
silicate.  T.  U.  crypt,  prism. 
Often  radiate.  Color  U.  brown  or 
green.  H=6.5. 

Piedmontite,  manganese  bearing 
epidote.  Color  reddish-brown, 
reddish-black.  (Mn,  1,  p.  47.) 

Continued  on  next  page. 


140 


DETERMINATIVE  MINERALOGY 


II — D.     Section  c. — Continued. 


Show  special  reactions.  Fuses  with  intumescence, 
swelling  or  cracking  apart. 

Insoluble  or  nearly  so  in 
HC1  or  HNO3.    Axinite 
gives  a  pale  green  flame 
color. 

TITANITE  (Sphene),  CaTiSiCK, 
M.  U.  hi  acute  crystals.  Color  U. 
brown  or  yellow.  Slightly  decom- 
posed by  acids.  Ti,  1,  p.  69. 

Axinite.  A  boro-silicate  of  Al  and 
Ca  (with  Fe  and  Mn).  Trie.  Crys- 
tals broad  and  acute.  H  =  6.7 
Boron,  1,  p.  31.  Gelatinizes  after 
fusion. 

Some  AMPHIBOLES.        PYROX- 
ENES may  intumesce.      (See  be- 
low.) 
Melilite    fuses    sometimes   with    in- 
tumescence. 

Tourmaline,  see  p.  127. 

Fuse  quietly,  or  with  little  intumescence.  Soluble 
in,  or  decomposed  by,  hot  dilute  acids,  with 
effervescence,  or  with  formation  of  a  residue. 

Soluble  in  dilute  HNO3  or 
HC1  with  effervescence, 
giving  a  green  solution. 
Chrysocolla       (see       be- 
yond)   frequently   effer- 
vesces    from     admixed 
malachite. 

MALACHITE,  CuCO3.Cu(OH)2. 
Color  green,  silky  luster.  Reduces 
readily  to  a  copper  globule. 
H=  3.5-4. 

AZURITE,  2CuCO3.Cu(OH)2.  M. 
U.  crystalline.  Color  blue.  Re- 
duces easily  to  copper  globule. 
H  =  3.5-4. 

Soluble   in   dilute   HNO3 
or  HC1  and  yield  gelat- 
inous silica  upon  evapo- 
ration. 

Troostita,  (Willemite)  (Zn,Mn)2SiO4. 
R.  U.  brown,  yellow,  or  green. 
(Zn,  2,  p.  75.  Mn,  1,  p.  47.) 

Tephroite.     Mn2SiO4.     U.  brown. 

Melilite.  Formula  uncertain,  Si,Al, 
Fe,Ca,Mg,Na.  Fuses  with  slight 
intumescence. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — D.     Section  c. — Continued. 


141 


Fuse  quietly  or  with  little  in- 
tumescence. Soluble  in,  or  de- 
composed by,  hot  dilute  acids 
with  formation  of  a  residue. 

Decomposed  in  boiling 
dilute  HNO3  or  HC1 
with  the  separation  of 
non-gelatinous  silica. 
Diff.  fusible. 

SERPENTINE,  H4Mg3Si2O9.  U. 
mass.  Color  green  or  yellowish- 
green.  Abundant  H2O  in  C.T. 
Varieties  based  on  structure  — 
Chrysotile  (Asbestos),  fibrous;  Pic- 
rolite,  splintery;  Antigorite,  foliated. 

Decomposed  by  HC1  with 
separation  of  a  yellow 
residue. 

Hiibnerite,  MnWO4.  Civ.  pine.  perf. 
Color  U.  brown.  W.  test,  p.  70. 
Sp.  G.=7+.  H  =  5-5.5. 

Soluble  in  dilute  acids,  but  without  effervescence,  or  the 
separation  of  silica,  or  other  residue. 

Color  red. 

CUPRITE,  Cu2O.  I.  Crystals  com- 
mon; also  fibrous  or  granular 
mass.  Reduces  easily  to  copper 
globule. 

Color  green.  React  for 
copper. 

Atacamite,  Cu2Cl(OH)3.  O.  U. 
cryst.  prismatic.  Color  emerald- 
green.  Azure-blue  flame.  Cl.  test. 

Brochantite,  CuSO4.3Cu(OH)2.  O. 
U.  cryst.  Emerald-green.  Sulphate 
test. 

Torbernite,      Cu(UO2)2(PO4)2.8H2O. 
T.   U.  Tabular  crystals.   Civ.  basal 
perf.     Color  emerald-green. 
Libethenite,      Cu(Cu.OH)PO4.      O. 
Dark  olive-green. 

Color  yellow. 

Autunite,  Ca(UO2)2(PO4)2.8H2O.  O. 
U.  tabular.  Uran.  test,  1,  p.  71. 

Continued  on  next  page. 


142  DETERMINATIVE  MINERALOGY 

II — D.     Section  c. — Continued. 


Soluble  in  hot  dilute 
acids.  —  Continued. 

Color  yellow. 

Carnotite.    A  potassium  urano-vana- 
date.  Soft,  loosely  coherent  powder. 
Often    in    sandstone.     U.    test,    2, 
p.  71,  V,  2,  p.  72. 

Colors  the  flame  red. 

Lithiophilite,       Li(Mn,Fe)PO4.      O. 
Civ.  basal  perf.     Color  salmon  or 
clove-brown.    Mn  test,  1,  p.  47. 

Insoluble  or  nearly  so  in  dilute  HNO3  or  HCI.  May  fuse  with  a 
little  intumescence. 

Very  soft  (H  =  l). 

TALC,  see  beyond,  p.  151. 

U.     crystalline;     dodeca- 
hedrons     or      trapezo- 
hedrons,    also   granular. 
Color      pink,      reddish- 
brown,    red,    dark    red. 
H  =  7.-7.5. 
Ca,    Mg,    Mn,    Fe    are 
isomorphous;     also    Al, 
Fe  and  Mn  in  the  garnet 
molecule.         Gelatinize 
after  fusion  B.B. 

GARNETS,   including  the  following 
varieties  : 
Grossularite,       essentially       Ca3Al2 

(Si04)3. 
Pyrope,    essentially    Mg3Al2(SiO4)3. 
Spessartite,  (Mn,Fe)  3Al2(SiO4)  3. 
Almandite,   FesAl2(SiO4)3    (common 
garnet)  . 

Reacts  for  Mn  in  borax 
bead.  (2,  p.  48.) 

Rhodonite,    MnSiO3.      Tri.      Color 
U.  red  or  pink,  also  brown.     Civ. 
prism,   perf.   at  nearly   90°.      The 
variety  Fowlerite  contains  zinc. 

Amphiboles,  Monoclinic 
crystallization  and  pris- 
matic in  habit.  Char- 
acterized by  a  fine  pris- 
matic cleavage  at  angles 
of55°andl25°.  H  =  5-6. 
Tests  for  bases,  4,  p.  58. 

Actinolite,    Ca(Mg,Fe)3Si4Oi2.    Pris- 
matic habit.    Color  green.    Sp.  G. 
3. 
HORNBLENDE.      Like  the  above, 
but  contains  Al.     Color  green  to 
black.     Sp.  G.  3.2-3.3. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — D.     Section  c. — Continued. 


143 


u 

Pyroxenes.     Crystals  are 

DIOPSIDE    (Malacolite), 

g 

Moncl.    in    habit,    with 

CaMgSi2O6.    Fe  isom.  w.  Mg,  and 

o  ^ 

nearly      square      cross- 

then  grades  towards  Hedenbergite. 

»  1 

section.     Often  show  a 

Colorless,  white,  pale  green.    Sp.  G. 

basal  parting.     H  =  5-6. 

3.29. 

3     | 

Tests  for  bases,  see  4, 

HEDENBERGITE,         CaFeSi2O6. 

1.1 

p.  58. 

Color  black.     Sp.  G.  3.5. 

.2     03 

AUGITE.    Like  the  above  but  con- 

§ 1 

tains  Al.     Sp.  G.  3.33-3.45. 

IS 

Greenish-black  to  black  color. 

If 

Common    pyroxene    of    lavas    and 

g  1 

igneous  rocks. 

it 

Difficultly  fusible.    Color 

lolite.  See  p.  152. 

fl 

blue  or  green. 

Tourmaline.     See  p.  153. 

Division  II.  SUBDIVISION  E.  The  mineral  is  infusible  B.B., 
non-volatile,  etc. 

Section  a.  The  minerals  are  white  or  become  so  on  ignition  B.B. 
The  fine  powder,  moistened  with  cobalt  nitrate  solution  and  intensely 
ignited  B.B.,  becomes  blue  (alumina  or  zinc  silicate). 


Give  gelatinous  silica  upon  evapora- 
tion with  acids.     (1,  p.  57.) 


Slowly  soluble  in  acids. 


CALAMINE,  (ZnOH)2SiO3.  O.  U. 
cryst.  in  radiating  groups.  Colorless 
white,  blue.  H  =  4.5-5.  (Zn.  test, 
2,  p.  75.) 

Allophane,  Al2SiO5.5H2O.  Amor- 
phous, wax-like.  H  =  3.  Sp.  G. 
1.88.  Crumbles  B.B. 


Wavellite, 
BAUXITE, 


See  below  under  next 
head. 


Continued  on  next  page. 


144  DETERMINATIVE  MINERALOGY 

II — E.     Section  a. — Continued. 


1 

*o 

1 

a 

I 

a 

8 

1  • 
1 

M 

1 

& 

o 

s 

1 

Very  soft,  H  =  1-2.5  H2O 
in  C.T. 

KAOLINITE,        H4Al2Si2O9.        U. 
amorphous,     compact    or    earthy. 
White      when      pure,      commonly 
stained  yellow  or  red,  often  impure. 
For  Halloysite,  see  Dana. 
Pyrophyllite,     H2Al2(SiO3)4.        Foli- 
ated, compact.       Civ.  basal  perf. 
U.  white  or  buff. 
Agalmatolite.  1 
Pagodite.         r  Mass,  in  structure. 
Finite. 
They  U.  react  for  potash  and  are 
massive,  impure  substances  related 
in  part  to  muscovite  and  in  part  to 
pyrophyllite.     See  Dana. 

Aggregates  of  radiating 
prisms  or  fibers.  White 
to  green  in  color. 

Wavellite  (A1.OH)3(PO4)2.5H2O. 
Slowly  decomposed  in  acids. 
P  test,  2  or  3,  pp.  52-3. 

Colorless,  but  U.  apple  to 
emerald  -green. 

Variscite,  A1PO4.2H2O.    U.  massive. 
P  test,  2  or  3,  pp.  52-3. 

Azure-blue,  pyramidal 
crystals. 

Lazulite,  (Mg,Fe)(Al.OH)2(PO4)2.  M. 
H  =  5-5.5     P  test,  2  or  3,  pp.  52-3. 

Color  blue  to  greenish- 
blue.  Fibrous  to  col- 
umnar aggregates. 

Dumortierite.     An    aluminium    sili- 
cate.    May  contain  boron.     H  =  7. 

U.  in  bladed  crystals.  Civ. 
pine.  perf.  j|  to  elonga- 
tion. 

CYANITE,  Al2SiO5.  Trie.   Scratches 
easily  ||  to  elongation.     Basal  part- 
ing.    Striated  ||  to  length. 

White.     Fibrous. 

Fibrolite,  Al2SiO=.  O.  Civ.  pine.  perf. 

Incrustations,  Stalactitic. 

Gibbsite,  A1(OH)3. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — E.     Section  a. — Continued. 


145 


Insoluble,  or  very  slowly  sol- 
uble in  hot  dilute  HCI  or 
HNO3.  Hardness  less 
than  that  of  steel 

Concretionary  structure, 
earthy,  also  compact. 

BAUXITE,  A12O3.XH2O.  White, 
brown,  reddish.  Often  impure. 

Massive  and  as  minute 
crystals. 

Alunite  (K,Na)(A1.2OH)3(SO4)2. 
Hex.  R.  Color  white. 

Massive,  or  consisting  of 
fine  scales.  Fuses  with 
diff.  Sodium  flame 
color. 

Pargonite,  Na2O.3Al2O3.6SiO2  2H2O. 
Soda  mica. 

Insoluble  in  hot  dilute  HNO3  or  HCI.  Hardness  greater  than  steel 
or  glass.  The  minerals  are  arranged  in  order  of  decreasing  hardness. 

Crystals  hex.  in  habit. 
Extremely  hard.  Vari- 
ous colors,  white,  gray, 
brown,  pink,  red,  blue. 

CORUNDUM,  A12O3.—  Hex.  rhomb. 
Commonly  shows  a  nearly  cubical 
parting  or  cleavage.  Cleav.  sur- 
faces striated  |j  to  edges.  H=9. 
Sp.  G.  3.9  to  4.1. 

Green  crystals,  various 
shades. 

Chrysoberyl,  BeAl2O4.  O.  H=8.5. 
Sp.  G.  =3.6-3.8.  Be  test,  p.  28. 

U.  as  octahedral  crys- 
tals. U.  dark  green  or 
gray,  sometimes  pink  or 
red. 

Spinel,  (Mg,Fe)Al2O4.  I.  Gahnite, 
or  zinc  spinel,  reacts  for  zinc  with 
Na-sCOs  and  carbon  B.B.  H=8+. 

U.  as  colorless  or  brown, 
orthorhombic  crystals. 

Topaz,  (AlF)2SiO4.  O.  Civ.  basal 
perf.  H  =  8.  Sp.  G.=3.55.  Flu- 
orine test,  2,  p.  40. 

U.  as  elongated  prisms. 
(Fibrous  form,  see  fibro- 
lite  above.) 

Sillimanite,  Al2SiO5.  O.  Civ.  pine, 
perf.  white,  brown.  H  =  7.  Sp.  G. 
3.2. 

U.  as  stout  rect.  prisms, 
in  mica  schist. 

ANDALUSITE  (Chiastolite), 
Al2SiO5.     O.     H  =  7.5. 
Commonly  contains  inclusions. 

Continued  on  next  page. 


146 


DETERMINATIVE  MINERALOGY 


II — E.     Section  a. — Continued. 


Insoluble  in  hot  dilute  HNO3  or  HCI.  Hardness 
greater  than  steel  or  glass.  The  minerals  are 
arranged  in  order  of  decreasing  hardness. 

Pink  to  nearly  colorless 
prisms  or  columnar  ag- 
gregates often  radiating 
and  U.  striated  longi- 
tudinally. 

Tourmaline,  a  borosilicate  of  Al  and 
other  elements.  R.  The  crystal 
cross-section,  is  often  triangular. 
Reacts  for  Boron,  1,  p.  31. 
H  =  7+. 

Trapezohedral  crystals. 
Decomposed  with  the 
separation  of  non-gel- 
atinous silica. 

LEUCITE,  KAlSi2O6.  I.  Occurs 
U.  as  embedded  gray  or  white  crys- 
tals in  basalt.  H  =  5.5-6.  Potash 
test,  b,  p.  53. 

Long,  bladed  crystals.  U. 
blue  or  green  in  color. 
Civ.  pine.  perf. 

CYANITE,  Al2Si05.  O.  H.  greater 
than  steel  in  a  direction  at  right 
angles  to  elongation  of  crystal. 

U.  in  flattened  crystals. 
Gives  water  in  C.T. 

Diaspore,  AIO(OH).  O.  Civ.  pine, 
perf.  Sol.  in  salt  of  phos.  bead. 
H  =  6. 

Blue,  pyramidal  crystals. 

Lazulite.     See  above.     H  =  5-5.5. 

II — E.     Sections  b  and  c. 


O    P£H 
rQ       £*> 

n 
O   ""^ 

g  "o 

p4    ^ 

'"  2 
pq  'o 

WJ 
III 

Red  streak. 

HEMATITE,  \  c 
Turgite,          ')  See  p.  115. 

Yellow  to  ochre-brown 
streak. 

LIMONITE,  1 
Goethite,         / 

Carbonates.  Effervesce  in 
hot  HCI  with  evolution 
of  CO  2.  When  crystal- 
line all  but  zaratite  pos- 
sess a  perf.  Rhomb, 
cleav. 

SIDERITE,  (Spathic  iron),  FeCO3. 
R.     Color  brown.    Weathered  sur- 
faces, often  rusty. 
Breunnerite,  (Mg,Fe)CO3.     R. 
Color  brown,  gray,  rarely  white. 
Ankerite,  Ca(Mg,Fe)(CO3.)2.  R. 
Color  brown,  gray,  rarely  white. 
RHODOCHROSITE.     See      below 
under    c.      May    contain    enough 
iron  to  become  magnetic. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — E.     Section  b. — Continued;    Section  c. 


147 


Carbonates. — Continued. 


Zaratite.  Hydrous  carbonate  of  Ni. 
Color  emerald-green.  U.  as  incrus- 
tations. (Ni  test,  1,  p.  50.) 


Sulphide.  Gives  off  hy- 
drogen sulphide  (odor) 
with  hot  HC1. 


Rhombohedral      Carbon- 
ates.   Civ.  easy  and  perf . 

1 1  to  three  equally  inclined 
directions    (Rhomb). 
H  =  3-4.5. 


SPHALERITE,  ZnS.  I.  Cleav.  in 
six  directions  perf.  Color  yellow  to 
brown,  also  reddish,  highly  lustrous. 
Zn  test,  2,  p.  72.  H  =  3.5-4. 


CALCITE,  CaCO3.  R.  Commonly 
in  fine  crystals  of  various  habits; 
also  granular,  compact.  Colorless, 
white  and  various  light  shades. 
Effervesces  freely,  even  in  very 
dilute  (1-20)HC1  or  HNO3.  H=3. 
Sp.  G.=2.72.  Chalk,  an  earthy 
variety. 

DOLOMITE,  CaMg(C03)2.  R. 
Crystals  and  cleav.  surfaces  often 
curved;  also  granular,  compact. 
Colors  varied,  U.  white,  pinkish, 
gray.  Little  or  no  effervescence  in 
cold  dilute  acids.  H  =  3.5-4. 
Sp.  G.  2.85.  Mg  test,  1,  p.  47. 

MAGNESITE,  MgCO3.  U.  cryst. 
also  massive.  U.  white,  gray  or 
light  brown.  H  =  3.5-4.5,  Sp.  G. 
=  3.  Mg  1,  p.  47. 

RHODOCHROSITE,  MnCO3.  R. 
Color  pink  to  red,  also  brown. 
H  =  3.5-4.5.  Sp.  G.=3.5.  Mn 
test,  1,  p.  47. 


Continued  on  next  page. 


148  DETERMINATIVE  MINERALOGY 

II — E.     Section  c. — Continued;  Section  d. 


- 

Rhombohedral       carbon- 

SMITHSONITE,    ZnCO3.       Often 

1 

ates  .  —  Continued. 

contaminated  with  iron,  copper,  etc. 

0 

R.    (See  Div.  II,  B.  g).   Botryoidal, 

w 

encrusted.     Colors  varied  in  light 

o 

shades.     H  =  5.     Sp.   G.   4.4.     (Zn 

0 

test,  1,  p.  74.) 

W 

Soft.     U.  white  and  mas- 

Hydrozincite,   3ZnO.CO2.2H2O, 

1 

sive. 

Massive,   often  encrusted,    earthy, 

3    . 

fibrous.  H2OinC.T.  Zntest,!  p.74. 

ll 

_<-j      CO 

Color  pale  green  or  blue. 

Aurichalcite,  2(Zn,Cu)CO3. 

S  .a 
c 

U.  acicular,  encrusted. 

3(Zn,Cu)(OH)2.     H=2     (Zn    test, 

1  * 

1,  p.  74.     Cu  test,  3,  p.  39.) 

§  e? 

Crystals,  and  in  columnar 

ARAGONITE,  CaCO3.     O.     Effer- 

[   ft 

or    acicular    aggregates. 

vesces    in    very    dilute    acids    like 

1  ^ 

Color  U.  white.    Cleav. 

calcite.     H  =  3.5-4.     Sp.  G.=2.95. 

.j3  & 

poor. 

Strontianite,  SrCO3.     O.     Yields  a 

o   t> 

crimson    flame    color.     H  =  3.5-4. 

^  « 

Sp.  G.=3.7.    Sr  test,  3,  p.  64. 

1 

Acicular,      tufted,      also 

Hydromagnesite,  3MgCO3.Mg(OH)2. 

•|i 

earthy. 

3H2O.     H  =  3.5.     Mg  test,  1  or  2, 

<T 

p.  47. 

For  other  rare  species,  see  B.  &  P.,  p.  289. 


Section  d.  Completely 
soluble  in  boiling  dil- 
ute HCI,  but  do  not 
yield  silica  upon  evap- 
oration nor  effervesce. 

U.  in  simple  hexagonal 
prismatic  crystals.  U. 
green  or  brown. 

APATITE,  Ca4(CaF)(PO4)3.  H. 
H  =  5.  Phosphate  test,  2,  p.  52. 
May  give  a  slight  effervescence. 

Color  U.  orange-red  or 
dark  red.  Streak  orange 
or  yellow. 

Zincite,  (Zn,Mn)O.  H  =  4+.  Cleav. 
basal  perf.  Zn  test,  1  or  2,  pp. 
74-5.  Mn  test,  1,  p.  47. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 


149 


II  —  E.     Section  d.  —  Continued;    Section  e. 


Section  d.  Completely 
soluble  in  boiling  di- 
lute HCI,  but  do  not 
yieldsilicauponevap- 
oration  nor  effervesce 

Cubes,  octahedrons,  also 
granular. 

Periclase,  MgO.  I.  Civ.  cubic, 
perf.  H  =  6.  Color  U.  white. 

U.  foliated.    Color  white. 

Soft. 

Brucite,  Mg(OH)2.  H.  Cleavage 
basal  perf.  H  =  2.  H2O  in  C.T. 

For  a  considerable  number  of  rare  minerals  which  fall  here,  Sulphates  and 
Phosphates  chiefly,  see  B.  &  P.,  pp.  290  to  293. 


Decomposes  with  the 
formation  of  a  bright 
yellow  residue  (tung- 
stic  oxide). 


Decomposed  with  separa- 
tion of  non-gelatinous 
silica.  2,  p.  58. 


Scheelite,  CaWO4.  T.  White,  yel- 
low, brown,  green.  H=  4-5.5. 
Sp.  G.  6.05.  W  test  1,  p.  70. 


SERPENTINE,  H4Mg3Si2O9.     See 
Div.  II.     D.     Section  c. 


LEUCITE,  KAlSi2O6.  I.  White  or 
colorless.  Trapezohedral  crystals. 
H  =  5.5-6.  K  test  1,  b,  p.  53. 


CHRYSOCOLLA,  CuSiO32H2O.  U. 
amorphous,  massive.  Color  bluish- 
green. 


Garnierite,  H4(Ni,Mg)2Si3O12.4H2O, 
but  variable.  Amorph.  botryoidal. 
Green  color.  Ni  test,  2  or  3,  p.  50-1. 


Deweylite    (Gymnite),   Hydrous   Mg 
silicate.    Amorphous. 


Continued  on  next  page. 


150 


DETERMINATIVE  MINERALOGY 


II — E.     Section  e. — Continued;  Section/. 


ill 

(S-2  ] 
.** 

<»  •" 

SS  !j3    of    § 
.0    <g  H3    £ 
**•*    o  "o    £* 

Decomposed    with    sepa- 
ration of  non-gelatinous 
silica.     2  p.  58. 

Sepiolite,  H4Mg2(Si3O10). 
(Meerschaum.)     Compact,  earthy. 
White  color.   Sp.  G.=2.   H=  2-2.5. 

Pollucite,  H2Cs4Al4(SiO3)9.     U.  mas- 
sive cryst.;  resembles  quartz. 

See  also  B.  &  P.,  p.  295,  for  other  species. 


Section  f.  Soluble  in  boiling  HCI  and  yield  gelantinous  silica 
upon  evaporation. 

Color  pale  green  or  yel- 
lowish-green. U.  gran- 
ular. 

CHRYSOLITE,  (Olivine)  (Mg,Fe)2 
SiO4.  O.  Found  in  basalts  and  cer- 
tain basic  rocks.  H=  6.5-7.  Must 
be  finely  powdered  to  yield  Silica 
gel.  Fe  and  Mg  tests,  4,  p.  58. 

Willemite,  (Zn,Mn)SiO4.  Hex.  R. 
React  for  zinc,  2,  p.  75. 

Color  emerald-green.  U. 
cryst. 

Dioptase,  H2CuSiO4.  Civ.  Rhomb, 
perf. 

U.  in  brown  or  reddish- 
brown  cryst.  grains. 

Chondrodite,Mg3[Mg(F,OH)](SiO4)2. 
Often  found  in  limestone.  Mg 
test,  1,  p.  47.  F  test,  1,  p.  39. 

B.B.  swells,  cracks,  and 
often  glows.  Color  black 
or  nearly  so. 

Gadolinite,  FeBe2Y2Si2O10.  H=6. 
5-7.  Sp.  G.  4.2-4.5.  Yttrium 
test,  p.  55. 

Sp.  G.  4.2-4.9.  React 
for  rare  earth  metals 

(p.  55). 

Thorite,  ThSiO4.    T.     Th  test,  p.  55. 

Cerite.  Hydrous  silicate  of  cerium 
and  iron.  Sp.  G.  4.9.  U.  massive. 

See  also  B.  &  P.,  p.  294  for  other  species. 


THE  DETERMINATION  OF  MINERALS 


151 


II — E.     Section    g.     Insoluble    or    practically    so    in    boiling 
HC1  or  HNO3. 


1 

• 

W 

J 

1 

Very    soft.     Soapy   feel. 

TALC,  H2Mg3(Si03)4.  M.  U. 
foliated,  fibrous,  or  massive.  White, 
gray,  green.  H  =  l. 

Micaceous  structure  (Ag- 
gregation of  easily  sepa- 
rable scales  or  plates. 
Large  crystals  yield 
sheets.) 

MICAS.  See  p.  138.  Sheets  are  flexi- 
ble and  elastic.  H  =  2.  Colorless, 
brown,  to  almost  black. 

The  CHLORITES.  Seepage  p.  138. 
Sheets  are  flexible,  but  not  elastic. 
H  =  2.  Color  green  to  almost 
black. 

Brittle  micas  (Chloritoid,  etc.). 
Hydrous,  silicates  of  Ca,  Mg  and 
Al.  Colors  green,  brown,  yellowish, 
reddish,  gray.  Margarite  is  pink. 
,The  leaves  or  flakes  are  brittle. 

Pale      to      deep      green. 
Amorphous,  botryoidal. 
Yellowish  to  reddish- 
brown  crystals.     Phos- 
phorus, 2,  p.  52.    Rare 
earths,  p.  55. 

Garnierite.     See  p.  149. 

Monazite,        (Ce,La,Di)PO4.        M. 
Often  found  as  rounded  grains  in 
sand.     H=  5-5.5. 
Xenotime,  YPO4.T.    U.  cryst.    Civ. 
prism,  perf. 

For  other  species,  see  B.  &  P.,  pp.  296  to  298. 


Hardness  equal 
or  greater  than 
steel. 

Color  black,  streak  brown. 

CHROMITE,         FeCr2O4         with 
MgAl2O4.     I.     Octahedral  crysts. 
Commonly      granular.       H=6-7. 
Cr  test,  1,  p.  36.     Sp.  G.=  4.2-4.5. 

Continued  on  next  page. 


152  DETERMINATIVE  MINERALOGY 

II — E.     Section  g. — Continued. 


Color  black,  brown,  red, 

RUTILE.  T.  Crystals  prism., 

reddish-brown.       React 

striated,  often  twinned.  H. 

for  titanium  (1,  p.  69). 

=  6-6.5.  Sp.  G.=4.18-4.25. 

Several  other  rare  com- 

Octahedrite.   T.  Crystals  U. 

TiO 

pounds  of  Ti  and  other 

acute  pyramids.     H  =  5.5- 

JL  Iv^2 

rare  elements  fall  here. 

6.   Sp.G.=  3.8-3.95. 

Brush  -  Penfield,       pp. 

Brookite,  O.  U.  cryst.  H  =  6. 

297-8. 

Sp.  G.=4.0. 

Perowskite,  CaTiO3.    I.    Commonly 

in  cubes  or  octahedrons.    H=5.5. 

Sp.  G.=4.03. 

1 

High       Sp.    G.  =  6.8-7.1. 

CASSITERITE    (Tinstone), 

SnO2. 

rt 

Color  U.  brown,  reddish- 

T.  Crystals  lustrous,  often  twinned. 

J 

brown  to  black. 

Occurs  often  in  botryoidal 

forms 

g 

and  as  grains  in  sand  (stream  tin). 

«t 

H  =  6-7.     Sn  test,  1,  p.  69. 

IH 
O 

Color  emerald-green. 

Uvarovite  (chrome-garnet),  Crystals, 

-a 

duodecahedral.  H  =  7.  Sp.  G 

=  3.4. 

i 

Chromium,  1,  p.  36. 

3 

6 

Color   green  or  turquois- 

Turquois,     H(A1.2OH)2PO4. 

Con- 

h 

blue. 

tains  copper  also.     Massive. 

H  =  6. 

1 

Phosphorus  test,  2,  p.  52. 

Color  light  to  dark  blue. 

lolite       (Cordierite).       H2(Mg,Fe)4 

Al8Sii0O37.  H  =  7-7.5.    Sp.  G. 

=  2.61. 

Possess  two  perf.   cleav- 

THE    FELDSPARS.       Orthoclase 

ages  at  right  angles  to 

and  Microcline.     See  p.   136.     U. 

each  other.  Diff.  fusible. 

White,  pink,  green.    H  =  6. 

Clear  or  frosted  crystals 

Diamond.    I.    Civ.  Oct.,  perf.  Color- 

(Oct.).     Grains  of  ex- 

less and  light  shades.    Rarely  black 

treme  hardness. 

and    amorphous.       H  =  10. 

Sp. 

G.  =  3.52. 

Continued  on  next  page. 


THE  DETERMINATION  OF  MINERALS 
II — E.     Section  g. — Continued. 


133 


Hardness  greater  than  steel 

Tetrag.  crystals,  U.  of 
simple  forms. 

ZIRCON,  ZrSiO4.  T.  H  =  7.5. 
Sp.  G.=4.68.  Color  U.  brown. 
Often  in  sands.  Zirconia  test,  1, 
p.  75. 

Yellow,  brown  to  black 
cryst.  grains. 

Baddeleyite  (Brazilite)  ZrO2. 
Zirkelite,    (Ca,Fe)O.2(Zr,Th,Ti)O2. 

Clear,  glassy,  also  white 
and  in  various  colors. 
Commonly  cryst.  in 
Hex.  well  terminated 
prisms.  Prisms  hori- 
zontally striated. 

QUARTZ,  SiO2.       Hex.       Rhomb. 
Conchoidal  fracture.   Also  granular 
compact.     Abundant  in  sand. 
The    powder    mixed    with    equal 
volumes  of  Na2CO3  yields  a  clear 
glass  B.B.     H  =  7.     Sp.  G.  =2.65. 

U.  in  simple  Hex.  prisms. 
U.  green  or  yellow  in 
color. 

Beryl,  Be3Al2(SiO3)6.  H  =7-7.5. 
Sp.  G.=  2.7-2.75.  Beryllium  test, 
p.  28.  U.  assoc.  with  quartz  and 
feldspar. 

Prismatic     crystals,     fre- 
quently      in    columnar 
aggregates.        Color  U. 
pink,  or  green  to  green-  < 
ish-black. 

TOURMALINE,  a  boro-silicate  of 
Al  and  other  elements.  Rhomb. 
Crysts.  U.  striated  and  of  hex.  or 
triangular  section.  H  =  7-7.5. 
Sp.  G.  =3-3.1.  Boron  test,  1,  p.  31. 

In  simple  ortho.  crystals; 
often  twinned.  Color 
reddish-brown,  brown  to 
black. 

STAUROLITE,  complex  silicate  of 
Fe  and  Al.  H  =  7-7.5  Sp.  G.  =  3.75- 
3.78. 

Yellow,  brown,  green  to 
black.  Become  black 
B.B.  Sometimes  slightly 
magnetic  (hypersthene). 

Enstatite,  MgSiO3.     O. 
Hypersthene,  (Mg,Fe)SiO3.     O. 
Constituents  of  basic  igneous  rocks. 
H  =  5-6.     Sp.  G.=3.1to3.3. 

Continued  on  next  page. 


154  DETERMINATIVE  MINERALOGY 

II — E.     Section  g. — Continued. 


*o3 
o 

Massive,  botryoidal,  stal- 

CHALCEDONY,  SiO2.     Reactions 

to 
•j 

actic,    encrusted,    wax- 

as  for  quartz.    H  =  7.    Sp.  G.  =  2.6- 

1 

like.     Various  colors. 

2.64.       Varieties.       Agate,     Flint, 

+3 
IH 
• 

Chert,  Jasper,  etc.     See  Dana. 

1 

Various  colors,  also  color- 

OPAL,       SiO2+  water.        (Hyalite, 

Ql 

• 

less.     Sometimes  shows 

colorless   opal),    Wood  opal,     Fire 

i 

a  play  of  colors.    Amor- 

opal.) H  =  5.5-6.5.  Sp.  G.  =2.1-2.2. 

I 

phous,  glassy. 

Yields    a    little    H2O    on    intense 

w 

ignition  B.B.  See  Dana. 

For  many  other  rare  minerals,  see  B.  &  P.,  pp.  298,  et 


seq. 


INDEX 


A 

Abbreviations,  vii 

Acanthite,  113 

Acids  (tests  with),  20 

Acmite,  127 

Actinolite,  142 

Adular  (orthoclase),  136 

Aegirite,  127 

Agamatolite,  144 

Agate  (var.  chalcedony),  154 

Alabandite,  114 

Alabaster  (see  Gypsum)  128 

Albite,  131,  136 

Allgodonite,  106 

Allanite,  113,  125,  139 

Allophane,  143 

Almandite,  127,  142 

Alkaline  reaction,  8 

Alum  (kalinite),  119 

Aluminium  (tests),  22 

Alunite,  145 

Alunogen,  119 

Amazonstone  (see  Microcline),  136 

Amblygonite,  135 

Amethyst  (var.  quartz),  153 

Amphiboles,  142 

Analcite,  130 

Anatase  (octahedrite),  152 

Andalusite,  145 

Andradite,  125 

Anglesite,  123 

Anhydrite,  128 

Ankerite,  125,  146 

Annabergite,  121 


Anorthite,  133 

Anthophyllite,  128 

Anthracite,  34 

Antigorite,  141 

Antimony  glance  (stibnite),  107 

(mineral),  107 

oxides,  24,  121 

oxysulphide,  121 

sulphide,  107 

tests,  23 
Apatite,  148 
Apophyllite,  134 
Aquamarine  (beryl),  153 
Aragonite,  148 
Arfvedsonite,  127 
Argentite,  113 
Argyrodite,  41 
Arsenates  (tests),  26 
Arsenic  (mineral),  106 

oxide,  25,  121 

sulphides,  121 

tests,  25 
Arsenolite,  121 
Arsenopyrite,  106 
Asbestos  (serpentine),  141 

(tremolite),  132 
Astrophyllite,  125 
Atacamite,  141 
Augite,  143 
Aurichalcite,  148 
Autunite,  141 
Axinite,  140 
Awaruite,  115 
Azurite,  140 


155 


156 


INDEX 


B 

Baddeleyite,  153 

Barite,  129 

Barium  carbonate,  129 

sulphate,  129 

tests,  27 
Barytes,  129 
Bauxite  (Beauxite),  145 
Bead  tests,  14,  83-86 
Beryl,  137,  153 
Beryllium  (tests),  28 
Beryllonite,  135 
Biotite,  138 
Bismuth  carbonates,  123 

flux,  30 

glance,  109 

(mineral),  109 

oxide,  29 

sulphide,  109 

tests,  29 

Bismuthinite,  109 
Bismutite,  123 
Black  Jack  (sphalerite),  110 
Blend  (see  sphalerite) 
Blowpipe  flames,  1-4 
Boracite,  135 
Borax  beads,  15,  84 

flux,  11,  15 

(mineral),  120 
Bornite,  111 
Boron  (tests),  31 
Bournonite,  108 
Braunite,  117 
Breunnerite,  146 
Brittle  micas,  151 
Brochantite,  141 
Bromine  (test),  31 
Bromyrite,  124 

Bronzite  (var.  hypersthene)  153 
Brookite,  152 
Brucite,  149 


Cadmium  (tests),  32 

Calamine,  124,  143 

Calaverite,  111 

Calc  spar  (calcite),  147 

Calcite,  147 

Calcium  carbonate,  147 

fluoride,  129 

phosphate,  148 

silicate,  134 

sulphate,  33,  128 

tests,  32 

tungstate,  133 
Calomel,  121 
Cancrinite,  133 
Canfieldite,  41 
Capillary  pyrites,  112 
Carbon  (mineral),  104,  114 

tests,  34 

Carbonates  (tests),  34 
Carnallite,  119 
Carnotite,  142 
Cassiterite,  152 
Celestite,  129 
Cerargyrite,  124 
Cerite,  150 
Cerium  (tests),  55 
Cerussite,  123 
Chabasite,  134 
Chalcanthite,  119 
Chalcedony,  154 
Chalcocite,  113 
Chalcophyllite,  122 
Chalcopyrite,  112 
Chalk  (calcium  carbonate),  147 
Chamosite,  126 
Charcoal  (heating  on),  10 
Chert,  154 
Chiastolite,  145 
Childrenite,  126 
Chloanthite,  106 


INDEX 


157 


Chlorides,  119,  124 

Chlorine  (tests),  35 

Chlorite,  138 

Chlorotoid,  151 

Chondrodite,  150 

Chromic  iron,  116 

Chromite,  117,  151 

Chromium  (tests),  36 

Chrysoberyl,  145 

Chrysocolla,  149 

Chrysolite,  150 

Chrysophrase  (var.  chalcedony),  154 

Chrysotile,  141 

Cinnabar,  120 

Cinnamon    stone     (see    grosularite), 

142. 

Claudetite,  121 
Cleavage,  96 
Clinochlore,  138 
Closed  tube  tests,  16,  78-79 
Coals,  34,  104 
Cobalt  arsenate,  121 

arsenides,  etc.,  106 

bloom,  121 

glance  (cobaltite),  106 

nitrate  (tests),  86 

tests,  37 
Cobaltite,  106 

Coccolite  (var.  diopside),  132 
Colemanite,  135 
Coloradoite,  110 
Colored  solutions,  87 
Columbates,  117 
Columbite,  117 
Columbium,  51 
Conichalcite,  122 
Copiapite,  120 
Copper  carbonates,  140 

glance,  113 

gray  (tetrahedrite),  107 

(native),  111 

nickel  (niccolite),  106 

oxides,  111,  113,  141 


Copper  peacock  (bornite),  111 
pyrites,  112 
ruby  (cuprite),  111 
silicate,  149,  150 
sulphate,  119 
sulphides,  111,  113 
sulph-antimonite,  107 
sulph-arsenates,  105 
sulph-arsenites,  105 
tests,  38 

Cordierite,  152 

Corundum,  145 

Cotunnite,  121 

Covellite,  111 

Crocidolite,  127 

Crocoite,  123 

Cryolite,  128 

Cuprite,  111,  141 

Cyanite,  144 

Cylindrite,  108 

D 

Danburite,  130 
Datolite,  130 
Decrepitation,  7 
Descloizite,  123 
Desmine  (stilbite),  131 
Deweylite,  149 
Diallage  (var.  pyroxene),  143 
Diamond,  152 
Diaspore,  146 
Diopside,  132,  137 
Dioptase,  150 
Disthene  (cyanite),  144 
Dog-tooth  spar  (calcite),  147 
Dolomite,  147 
Domeykite,  106 
Dumortierite,  144 
Dyscrasite,  107 

E 

Egglestonite,  121 
Elaeolite  (nephelite),  130 


158 


INDEX 


Electrum,  LY1 
Embolite,  124 
Emerald  (beryl),  153 
Emery  (var.  corundum),  145 
Enargite,  105 
Endlichite,  122 
Enstatite,  153 
Epidote,  127,  139 
Epsomite,  119 
Erythrite,  121 


Fayalite,  126 

Feather-ore  (jamesonite),  108 
Feldspars,  130,  131,  136 
Ferberite,  114 
Fergusonite,  118 
Fibrolite,  144 
Flame  tests,  9,  19,  87 
Flint  (chalcedony),  154 
Fluorine  (tests),  39 
Fluorite,  129 
Fluorspar  (fluorite),  129 
Franckeite,  108 
Franklinite,  116 
Freibergite,  107 
Fusibility,  5 

G 

Gadolinite,  139,  150 
Gahnite  (zinc  spinel),  145 
Galena,  Galenite,  109 
Garnets,  125,  142 
Garnierite,  149,  151 
Gay-Lussite,  128 
Gehlenite,  133 
Genthite  (garnierite), 
Germanium  (tests),  41 
Gersdorffite,  106 
Gibbsite,  144 
Glaucodot,  106 
Glauconite,  128 


Glaucophane,  132 
Glucinium,  28 
Goethite,  116 
Gold  (native),  112 

tellurides,  111 

tests,  41 
Goslarite,  120 
Graphite,  114 

Gray  copper  (tetrahedrite),  107 
Grossular  (ite),  137,  142 
Gymnite,  149 
Gypsum,  128 


Halite,  119 
Hardness,  96 
Hausmannite,  117 
Haiiynite,  133 
Heavy  spar,  129 
Hematite,  115 

Hemimorphite  (calamine),  143 
Herderite,  135 
Hessite,  111 
Heulandite,  134 
Hornblende,  142 
Horn  silver  (cerargyrite),  124 
Hiibnerite,  141 
Hyalite  (opal),  154 
Hydrogen,  41 
Hydromagnesite,  148 
Hydrozincite,  148 
Hypersthene,  153 


Iceland  spar  (calcite),  147 
Ilmenite,  116 
Ilvaite,  113,  126 
Intumescence,  7 
Iodine  (tests),  42 
lodyrite,  124 
lolite,  152 
Iridosmine,  114 


INDEX 


159 


Iron  carbonate,  125,  146 
native,  115 
niobate,  117 
oxides,  115,  116 
phosphate,  126 
pyrite,  112 
sulphate,  119 
sulphides,  112 
tantalate,  117 
tests,  42 
tungstate,  114 


Jadeite  (jade),  132 
Jamesonite,  108 
Jarosite,  126 
Jasper,  154 


K 


Kainite,  119 
Kalinite,  119 
Kaolin  (ite),  144 
Kermesite,  121 
Krennerite,  111 


Labradorite,  130 

Lapis-lazuli  (lazurite),  133 

Laumontite,  133 

Lazulite,  144 

Lazurite,  133 

Lead  arsenates,  122 
carbonate,  123 
cloro-carbonate,  122 
chromate,  36,  123 
glance  (galena),  109 
mineral,  109 
molybdate,  123 
phosphate,  123 
sulphantimonites,  108 
sulpharsenites,  105 
sulphate,  46,  123 


Lead  sulphide,  109 

tests,  44 

vanadate,  73,  123 
Lepidolite,  131 
Lepidomelane,  125 
Leucite,  146,  149 
Leucopyrite,  106 
Libethenite,  141 
Limonite,  116 
Linnaeite,  113 
Lithia-mica,  131 
Lithophylite,  142 
Lithium  phosphate,  142 

silicates,  131,  136 

tests,  46 

Loadstone  (magnetite),  115 
Lollingite,  106 
Lorandite,  121 


M 

Magnesite,  147 
Magnesioferrite,  115 
Magnesium  carbonates,  147 

hydroxide,  149 

oxide,  149 

sulphate,  119 

tests,  47 
Magnetic  iron  ore,  115 

properties,  9,  99 

pyrites  (pyrrhotite),  112 
Magnetite,  115 
Malachite,  140 

Malacolite  (var.  diopside),  132 
Manganese  carbonate,  125 

hydrates,  117 

niobate,  117 

oxides,  117 

phosphate,  126 

sulphide,  114 

tests,  47 

tungstate,  114,  141 
Manganite,  117 


160 


INDEX 


Marcasite,  112 

Margarite,  135 

Mascagnite,  121 

Meerschaum,  150 

Melanconite,  113 

Melanterite,  119 

Melilite,  140 

Menaccanite  (var.  ilmenite),  116 

Mercury  chloride,  121 

sulphide,  48,  120 

tests,  48 
Mesolite,  133 
Metallic  globules,  11,  77 

luster,  93 
Miargyrite,  107 
Mica,  iron,  125 

lime,  135 

lithia,  131 

magnesia,  138 

magnesia-iron,  138 

potash,  135 
Microcline,  136 
Millerite,  112 
Mimetite,  122 
Mirabilite,  119 
Mispickel  (arsenopyrite),  106 
Mohawkite,  106 
Molybdate  (mineral),  123 
Molybdates  (tests),  49 
Molybdenum  oxide,  49 

sulphide,  49,  110 

tests,  49 

Molybdenite,  110 
Molybdite,  124 
Monazite,  151 
Muscovite,  135 


N 


Natrolite,  130 
Natron,  119 
Nephelite,  130 
Niccolite,  106 


Nickel  arsenate,  121 
arsenide,  106 
silicate,  149 
sulphide,  112 
tests,  50 
Nigrine,  118 
Niobates,  117,  118 
Niobium  (tests),  51 
Niter,  120 
Nitrates,  51,  120 
Nitrogen  (tests),  51 
Noselite  (nosean),  133 


O 

Octahedrite,  152 
Oligoclase,  131,  136 
Olivenite,  122 
Olivine,  150 
Onyx  (chalcedony),  154 

Mexican  (calcite),  147 
Opal,  154 

Open  tube  tests,  18,  79-81 
Orpiment,  121 
Orthoclase,  136 
Osmic  oxide,  79 
Oxygen  (tests),  52 


Pagodite,  144 
Paragonite,  145 
Pearcite,  105 
Pectolite,  133 
Pennine  (penninite),  138 
Penninite,  138 
Pentlandite,  112 
Periclase,  149 
Peridote  (olivine),  150 
Perowskite,  152 
Petalite,  136 
Petzite,  111 
Pharmacosiderite,  121 


INDEX 


161 


Phlogopite,  138 
Phosgenite,  122 
Phosphates  (tests),  52 
Phosphorus  (tests),  52 
Picrolite,  141 
Piedmontite,  139 
Finite,  144 

Plagioclases,  130,  131,  133 
Platinum  arsenide,  106 

native,  114 

tests,  53 

Pleonaste  (var.  Spinel),  145 
Polianite,  117 
Pollucite,  150 
Polyargyrite,  107 
Polybasite,  107 
Polydymite,  113 
Potash  alum  (kalinite),  119 
Potassium  chloride,  119 

nitrate,  120 

tests,  53 
Prehnite,  134 
Proustite,  122 
Psilomelane,  117 
Pyrargyrite,  107 
Pyrite,  112 
Pyrite(s),  arsenical,  106 

capillary,  112 

copper,  112 

iron,  112 

magnetic,  112 

tin,  110 

white  iron,  112 
Pyrolusite,  114 
Pyromorphite,  123 
Pyrope,  142 
Pyrophyllite,  144 
Pyroxenes,  132,  137,  143,  153 
Pyrrhotite,  112 


Q 


Quartz,  153 


R 

Rare  earths  (tests),  55 

Realgar,  121 

Reduction  (of  metals),  11 

Residues  in  acids,  88 
closed  tube,  78 
open  tube.  81 

Rhodochrosite,  125,  146,  147 

Rhodonite,  142 

Riebeckite,  113,  127 

Ripidolite,  138 

Roasting,  13 

Roscoelite,  138 

Ruby  (corundum),  145 
copper  (cuprite),  141 
silver  (proustite),  122 
zinc  (zincite),  124 

Rutile,  152 


S 

Sal  Ammoniac,  121 
Salt,  119 

Salt  of  phosphorus  beads,  15,  85 
Saltpeter  (niter),  120 
Samarskite,  114 
Sassolite,  120 
Satin  spar  (gypsum),  128 
Scale  of  fusibility,  6 
Scapolite  (wernerite),  134 
Scheelite,  133,  149 
Scolecite,  133 
Scorodite,  121 
Sellenides,  111 
Selenite  (gypsum),  128 
Selenium  (tests),  57 
Senarmontite,  121 
Sepiolite,  150 
Serpentine,  141,  149 
Siderite,  125,  146 
Silicates  (tests),  57 
Silicon,  57 

oxide,  153,  154 


162 


INDEX 


Sillimanite,  145 
Silver  assay,  61 

bromide,  124 

chloride,  63,  124 

glance,  113 

iodide,  124 

native,  113 

sulphantimonites,  107 

sulpharsenites,  108,  122 

sulphides,  113 

tellurides,  111 

tests,  60 
Smaltite,  106 
Smithsonite,  124,  148 
Soapstone  (talc),  139 
Soda  (see  Sodium  carbonate) 
Soda  niter,  120 
Sodalite,  130 
Sodium  carbonate  beads,  15,  86 

carbonate,  119 

chloride,  119 

flux,  11,  15 

nitrate,  120 

sulphate,  119 

tests,  63 

Spathic  iron  (siderite),  125,  146 
Specular  iron,  115 
Specularite,  115 
Spessartite,  142 
Sperlylite,  106 
Sphalerite,  110,  124,  147 
Sphene  (titanite),  140 
Spinel,  145 
Spodumene,  131 
Stannite,  110 
Staurolite,  153 
Steatite  (talc),  139 
Stephanite,  107 
Sternbergite,  112 
Stibnite,  107 
Stilbite,  131,  134 
Stilpnomelane,  126 
Streak,  92 


Stromeyerite,  113 
Strontianite,  148 
Strontium  carbonate,  148 

tests,  64 

sulphate,  129 
Sublimates,  10,  12,  17,  18 

charcoal,  81-82 

closed  tube,  78-79 

iodine,  83 

open  tube,  80 

plaster,  82-83 
Sulphates  (tests),  66 
Sulphides  (tests),  64 
Sulphur  (native),  121 

tests,  64 
Sylvanite,  111 
Sylvite,  119 


Talc,  139,  151 
Tantalates,  117 
Tantalum  (tests),  67 
Tantalite,  67,  117 
Tellurides,  111 
Tellurium  (mineral),  110 

tests,  68 
Tennantite,  105 
Tenorite,  113 
Tephroite,  140 
Terlinguaite,  121 
Tetradymite,  110 
Tetrahedrite,  107 
Thallium  (flame),  87 
Thenardite,  119 
Thomsonite,  133 
Thorite,  150 
Thorium  (tests),  69 
Tin  oxide  (cassiterite),  152 

pyrites,  110 

stone  (cassiterite),  152 

tests,  69 
Titanic  iron  ore,  115,  116 


INDEX 


163 


Titanite,  140 
Titanium  oxides,  152 

tests,  69 
Topaz,  145 
Torbernite,  141 

Tourmaline,  113,  127,  136,  146,  153 
Tremolite,  131,  137 
Triplite,  126 
Triphylite,  126 
Trona,  119 
Troostite,  140 
Tungsten  (tests),  70 
Turgite,  115 
Thuringite,  126 
Turquois,  152 

U 

Ulexite,  131 
Uraninite,  118 
Uranium  (tests),  71 
Uvarovite,  152 


Valentinite,  121 
Vanadinite,  123 
Vanadium  (tests),  72 
Variscite,  144 
Vermiculites,  139 
Vesuvianite,  139 
Vivianite,  126 


W 

Wavellite,  143,  144 
Water  (tests),  73 
Wernerite,  134 
Whitneyite,  106 
Willemite,  124,  140,  150 
Witherite,  129 
Wolfram  (see  Tungsten) 
Wolframite,  114 
Wollastonite,  134 
Wulfenite,  123 


Yttrium  earths,  55 


Zaratite,  147 

Zinc,  carbonate,  124,  148 

oxide,  114 

silicates,  124,  140,  143 

sulphate,  120 

sulphide,  110,  124,  147 

tests,  74 

Zinc  blend  (sphalerite),  110,  124,  147 
Zincite,  124,  148 
Zircon,  153 
Zirconium  silicate,  153 

tests,  75 
Zirkelete,  153 
Zoisite,  136 


14  DAY  USE 

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APR  15  1964 


~UV 


LD  21-50m-6,'60 
(B1321slO)476 


General  Library 

University  of  California 

Berkeley 


